id: Q1XHL7 gene_symbol: grk7b product_type: PROTEIN status: COMPLETE taxon: id: NCBITaxon:7955 label: Danio rerio description: grk7b (GRK7-2) is one of two zebrafish paralogs of the cone-type G protein-coupled receptor kinase GRK7, an AGC-family serine/threonine kinase with an N-terminal RGS homology domain and a C-terminal geranylgeranylated cysteine that anchors it to photoreceptor membranes. Recombinant Grk7b phosphorylates light-activated rhodopsin (EC 2.7.11.14), the reaction that initiates opsin deactivation and arrestin binding during photoresponse shutoff and light adaptation. Its transcript is enriched in UV cones, and it is also expressed in the pineal organ and brain, whereas the paralog grk7a serves the other cone subtypes and is the kinase whose knockdown delays cone recovery and pineal parapinopsin inactivation; a distinct in vivo role for grk7b has not yet been demonstrated. existing_annotations: - term: id: GO:0005737 label: cytoplasm evidence_type: IBA original_reference_id: GO_REF:0000033 review: summary: Cytoplasm (is_active_in) from the family-wide PAINT node PTN001219785, seeded by Drosophila Gprk and a human GRK. action: KEEP_AS_NON_CORE reason: Not wrong - the outer-segment disc membranes where opsin kinases act lie within the cytoplasm - but grk7b is a C-terminally geranylgeranylated membrane-anchored kinase (UniProt LIPID feature; SUBCELLULAR LOCATION Membrane), so the informative location is the membrane, already annotated. Kept as non-core; no target-specific reason to contest the node placement. supported_by: - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:SUBCELLULAR LOCATION"] supporting_text: |- SUBCELLULAR LOCATION: Membrane - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["FT:LIPID"] supporting_text: |- /note="S-geranylgeranyl cysteine" qualifier: is_active_in supporting_entities: - FB:FBgn0261988 - PANTHER:PTN001219785 - UniProtKB:P32298 - term: id: GO:0009966 label: regulation of signal transduction evidence_type: IBA original_reference_id: GO_REF:0000033 review: summary: Regulation of signal transduction, placed by PAINT at the GRK-family node PTN001219785 (GRK1-7 across vertebrates and Drosophila Gprk). action: ACCEPT reason: |- At the family node the term is correct: every GRK phosphorylates activated GPCRs to desensitise signalling, and grk7b phosphorylates light-activated rhodopsin in vitro [PMID:16787417], consistent with the UniProt FUNCTION (photoresponse shutoff via cone opsin phosphorylation). The specific child that human GRK7 carries, GO:0016059 negative regulation of opsin-mediated signaling pathway, is not proposed for grk7b because the only in vivo test of this paralog (pineal parapinopsin inactivation) was negative [PMID:33579376] and the retinal in vivo work concerns grk7a [PMID:16039565]. Accepted at the node's level of specificity. supported_by: - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:FUNCTION"] supporting_text: Retina-specific kinase involved in the shutoff of the photoresponse and adaptation to changing light conditions via cone opsin phosphorylation, including rhodopsin (RHO). - reference_id: PMID:16787417 supporting_text: we focused on the opsin deactivation process initiated by G protein-coupled receptor kinase (GRK) 1 and GRK7 in the zebrafish - reference_id: PMID:33579376 supporting_text: We found that GRK7a knockdown slowed recovery of the response of parapinopsin photoreceptor cells, whereas GRK1b knockdown or GRK7b knockdown did not have a remarkable effect, suggesting that GRK7a, a cone-type GRK, is mainly responsible for inactivation of the parapinopsin photoproduct in zebrafish larvae. - reference_id: file:DANRE/grk7b/grk7b-deep-research-falcon.md supporting_text: A high-confidence, gene-specific finding is that **grk7b is enriched in adult UV cones**. qualifier: involved_in supporting_entities: - FB:FBgn0261988 - MGI:MGI:1347078 - PANTHER:PTN001219785 - RGD:61858 - RGD:61985 - RGD:61986 - UniProtKB:P32298 - UniProtKB:P43250 - UniProtKB:Q15835 - ZFIN:ZDB-GENE-081105-95 - term: id: GO:0050254 label: rhodopsin kinase activity evidence_type: IBA original_reference_id: GO_REF:0000033 review: summary: |- Rhodopsin kinase activity (EC 2.7.11.14): ATP-dependent phosphorylation of light-activated opsin. grk7b is GRK7-2 of Wada et al., one of the two zebrafish GRK7 paralogs. action: ACCEPT reason: PAINT node PTN002806910 (GRK1/GRK7 subfamily, seeded by human GRK7 Q8WTQ7 and both zebrafish grk7 paralogs) is the right node, and grk7b has its own IDA from the same source paper, so the target appearing in WITH/FROM is expected. Core activity [PMID:16787417]. supported_by: - reference_id: PMID:16787417 supporting_text: The recombinant GRKs phosphorylated light-activated rhodopsin, and the Vmax value of the major cone subtype, GRK7-1, was 32-fold higher than that of the rod kinase, GRK1A. - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:FUNCTION"] supporting_text: Retina-specific kinase involved in the shutoff of the photoresponse and adaptation to changing light conditions via cone opsin phosphorylation, including rhodopsin (RHO). qualifier: enables supporting_entities: - PANTHER:PTN002806910 - UniProtKB:Q8WTQ7 - ZFIN:ZDB-GENE-030904-3 - ZFIN:ZDB-GENE-050824-1 - term: id: GO:0004672 label: protein kinase activity evidence_type: IEA original_reference_id: GO_REF:0000002 review: summary: |- protein kinase activity: broad kinase parent term from InterPro/ARBA signatures (protein kinase domain, AGC kinase, GPCR-kinase family). action: MODIFY reason: Correct but uninformative; the specific activity demonstrated for the zebrafish protein is rhodopsin kinase activity [PMID:16787417], already annotated by IDA/IBA. Modify to GO:0050254. proposed_replacement_terms: - id: GO:0050254 label: rhodopsin kinase activity supported_by: - reference_id: PMID:16787417 supporting_text: The recombinant GRKs phosphorylated light-activated rhodopsin, and the Vmax value of the major cone subtype, GRK7-1, was 32-fold higher than that of the rod kinase, GRK1A. - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:FUNCTION"] supporting_text: Retina-specific kinase involved in the shutoff of the photoresponse and adaptation to changing light conditions via cone opsin phosphorylation, including rhodopsin (RHO). qualifier: enables supporting_entities: - InterPro:IPR008271 - term: id: GO:0004674 label: protein serine/threonine kinase activity evidence_type: IEA original_reference_id: GO_REF:0000002 review: summary: |- protein serine/threonine kinase activity: broad kinase parent term from InterPro/ARBA signatures (protein kinase domain, AGC kinase, GPCR-kinase family). action: MODIFY reason: Correct but uninformative; the specific activity demonstrated for the zebrafish protein is rhodopsin kinase activity [PMID:16787417], already annotated by IDA/IBA. Modify to GO:0050254. proposed_replacement_terms: - id: GO:0050254 label: rhodopsin kinase activity supported_by: - reference_id: PMID:16787417 supporting_text: The recombinant GRKs phosphorylated light-activated rhodopsin, and the Vmax value of the major cone subtype, GRK7-1, was 32-fold higher than that of the rod kinase, GRK1A. - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:FUNCTION"] supporting_text: Retina-specific kinase involved in the shutoff of the photoresponse and adaptation to changing light conditions via cone opsin phosphorylation, including rhodopsin (RHO). qualifier: enables supporting_entities: - InterPro:IPR000961 - term: id: GO:0005524 label: ATP binding evidence_type: IEA original_reference_id: GO_REF:0000002 review: summary: ATP binding from the protein-kinase ATP-binding-site signatures (IPR000719/IPR017441); UniProt annotates the ATP-binding loop (193-201) and Lys-216. action: KEEP_AS_NON_CORE reason: True of any active kinase and required for the rhodopsin-phosphorylation reaction [PMID:16787417], but it is a substrate-binding descriptor rather than the function. Kept as non-core. supported_by: - reference_id: PMID:16787417 supporting_text: The recombinant GRKs phosphorylated light-activated rhodopsin, and the Vmax value of the major cone subtype, GRK7-1, was 32-fold higher than that of the rod kinase, GRK1A. - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:FUNCTION"] supporting_text: Retina-specific kinase involved in the shutoff of the photoresponse and adaptation to changing light conditions via cone opsin phosphorylation, including rhodopsin (RHO). qualifier: enables supporting_entities: - InterPro:IPR000239 - InterPro:IPR000719 - InterPro:IPR000961 - InterPro:IPR017441 - term: id: GO:0007165 label: signal transduction evidence_type: IEA original_reference_id: GO_REF:0000002 review: summary: Signal transduction from the GPCR-kinase InterPro signature (IPR000239). action: MARK_AS_OVER_ANNOTATED reason: |- GRK7 kinases terminate rather than transmit the opsin signal; the gene's role is captured by the accepted regulation-of-signal-transduction IBA and by rhodopsin kinase activity [PMID:16787417]. The broad process term is not false but adds nothing and over-states an 'involved_in' role in signalling itself; marked over-annotated rather than removed. supported_by: - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:FUNCTION"] supporting_text: Retina-specific kinase involved in the shutoff of the photoresponse and adaptation to changing light conditions via cone opsin phosphorylation, including rhodopsin (RHO). - reference_id: PMID:16787417 supporting_text: we focused on the opsin deactivation process initiated by G protein-coupled receptor kinase (GRK) 1 and GRK7 in the zebrafish qualifier: involved_in supporting_entities: - InterPro:IPR000239 - term: id: GO:0016020 label: membrane evidence_type: IEA original_reference_id: GO_REF:0000044 review: summary: |- Membrane, lipid-anchored: UniProt SUBCELLULAR LOCATION by similarity to carp GRK7 (Q8WMV0), with a C-terminal S-geranylgeranyl cysteine. action: ACCEPT reason: UniProtKB-SubCell SL-0162 mapping. Consistent with the prenylation site and with GRK7 paralogs acting on opsins in photoreceptor outer-segment membranes; the zebrafish immunolocalisation of GRK7-1 to cone outer segments [PMID:16787417] and the anti-Grk7 antibody used later recognises both paralogs [PMID:30372740], so paralog-specific localisation of Grk7b itself remains to be shown. Accepted as the core site of action. supported_by: - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:SUBCELLULAR LOCATION"] supporting_text: |- SUBCELLULAR LOCATION: Membrane - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["FT:LIPID"] supporting_text: |- /note="S-geranylgeranyl cysteine" - reference_id: PMID:16787417 supporting_text: In situ hybridization and immunohistochemical studies localized both GRK1B and GRK7-1 in the cone outer segments and GRK1A in the rod outer segments. qualifier: located_in supporting_entities: - UniProtKB-SubCell:SL-0162 - term: id: GO:0050254 label: rhodopsin kinase activity evidence_type: IEA original_reference_id: GO_REF:0000120 review: summary: |- Rhodopsin kinase activity (EC 2.7.11.14): ATP-dependent phosphorylation of light-activated opsin. grk7b is GRK7-2 of Wada et al., one of the two zebrafish GRK7 paralogs. action: ACCEPT reason: Rhea:23356/EC 2.7.11.14 mapping of the UniProt CATALYTIC ACTIVITY, which is itself experimentally sourced from the zebrafish recombinant-kinase assay [PMID:16787417]. Core activity. supported_by: - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:FUNCTION"] supporting_text: Retina-specific kinase involved in the shutoff of the photoresponse and adaptation to changing light conditions via cone opsin phosphorylation, including rhodopsin (RHO). - reference_id: PMID:16787417 supporting_text: The recombinant GRKs phosphorylated light-activated rhodopsin, and the Vmax value of the major cone subtype, GRK7-1, was 32-fold higher than that of the rod kinase, GRK1A. qualifier: enables supporting_entities: - RHEA:23356 - EC:2.7.11.14 - term: id: GO:0016020 label: membrane evidence_type: ISS original_reference_id: GO_REF:0000024 review: summary: |- Membrane, lipid-anchored: UniProt SUBCELLULAR LOCATION by similarity to carp GRK7 (Q8WMV0), with a C-terminal S-geranylgeranyl cysteine. action: ACCEPT reason: Transfer from carp GRK7 (Q8WMV0). Consistent with the prenylation site and with GRK7 paralogs acting on opsins in photoreceptor outer-segment membranes; the zebrafish immunolocalisation of GRK7-1 to cone outer segments [PMID:16787417] and the anti-Grk7 antibody used later recognises both paralogs [PMID:30372740], so paralog-specific localisation of Grk7b itself remains to be shown. Accepted as the core site of action. supported_by: - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:SUBCELLULAR LOCATION"] supporting_text: |- SUBCELLULAR LOCATION: Membrane - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["FT:LIPID"] supporting_text: |- /note="S-geranylgeranyl cysteine" - reference_id: PMID:16787417 supporting_text: In situ hybridization and immunohistochemical studies localized both GRK1B and GRK7-1 in the cone outer segments and GRK1A in the rod outer segments. qualifier: located_in supporting_entities: - UniProtKB:Q8WMV0 - term: id: GO:0050254 label: rhodopsin kinase activity evidence_type: ISS original_reference_id: GO_REF:0000024 review: summary: |- Rhodopsin kinase activity (EC 2.7.11.14): ATP-dependent phosphorylation of light-activated opsin. grk7b is GRK7-2 of Wada et al., one of the two zebrafish GRK7 paralogs. action: ACCEPT reason: Manual transfer from human GRK7 (Q8WTQ7); redundant with, and consistent with, the direct zebrafish assay [PMID:16787417]. Core activity. supported_by: - reference_id: PMID:16787417 supporting_text: The recombinant GRKs phosphorylated light-activated rhodopsin, and the Vmax value of the major cone subtype, GRK7-1, was 32-fold higher than that of the rod kinase, GRK1A. - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:FUNCTION"] supporting_text: Retina-specific kinase involved in the shutoff of the photoresponse and adaptation to changing light conditions via cone opsin phosphorylation, including rhodopsin (RHO). qualifier: enables supporting_entities: - UniProtKB:Q8WTQ7 - term: id: GO:0050254 label: rhodopsin kinase activity evidence_type: IDA original_reference_id: PMID:16787417 review: summary: |- Rhodopsin kinase activity (EC 2.7.11.14): ATP-dependent phosphorylation of light-activated opsin. grk7b is GRK7-2 of Wada et al., one of the two zebrafish GRK7 paralogs. action: ACCEPT reason: Abstract-only cache, but the abstract states that the recombinant zebrafish GRKs (which include GRK7-2 = grk7b) phosphorylated light-activated rhodopsin, and UniProt records both Rhea reactions for Q1XHL7 from this paper (ECO:0000269). Core activity. In vivo, grk7b knockdown had no remarkable effect on parapinopsin photoresponse inactivation in the pineal, whereas grk7a knockdown did [PMID:33579376], and the retinal cone-recovery phenotypes are grk7a knockdowns [PMID:16039565]; grk7b is the UV-cone-enriched paralog [PMID:34462505]. supported_by: - reference_id: PMID:16787417 supporting_text: Screening of the ocular cDNAs identified two homologs for each of GRK1 (1A and 1B) and GRK7 (7-1 and 7-2), and they were classified into three GRK subfamilies, 1 A, 1B and 7 by phylogenetic analysis. - reference_id: PMID:16787417 supporting_text: The recombinant GRKs phosphorylated light-activated rhodopsin, and the Vmax value of the major cone subtype, GRK7-1, was 32-fold higher than that of the rod kinase, GRK1A. - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:FUNCTION"] supporting_text: Retina-specific kinase involved in the shutoff of the photoresponse and adaptation to changing light conditions via cone opsin phosphorylation, including rhodopsin (RHO). qualifier: enables - term: id: GO:0004703 label: G protein-coupled receptor kinase activity evidence_type: IEA original_reference_id: GO_REF:0000120 qualifier: enables supporting_entities: - ARBA:ARBA00034192 - InterPro:IPR000239 review: summary: |- G protein-coupled receptor kinase activity: broad kinase parent term from InterPro/ARBA signatures (protein kinase domain, AGC kinase, GPCR-kinase family). action: MODIFY reason: Correct but uninformative; the specific activity demonstrated for the zebrafish protein is rhodopsin kinase activity [PMID:16787417], already annotated by IDA/IBA. Modify to GO:0050254. proposed_replacement_terms: - id: GO:0050254 label: rhodopsin kinase activity supported_by: - reference_id: PMID:16787417 supporting_text: The recombinant GRKs phosphorylated light-activated rhodopsin, and the Vmax value of the major cone subtype, GRK7-1, was 32-fold higher than that of the rod kinase, GRK1A. - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:FUNCTION"] supporting_text: Retina-specific kinase involved in the shutoff of the photoresponse and adaptation to changing light conditions via cone opsin phosphorylation, including rhodopsin (RHO). references: - id: GO_REF:0000002 title: Gene Ontology annotation through association of InterPro records with GO terms findings: [] - id: GO_REF:0000024 title: Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence similarity findings: [] - id: GO_REF:0000033 title: Annotation inferences using phylogenetic trees findings: [] - id: GO_REF:0000044 title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt findings: [] - id: GO_REF:0000120 title: Combined Automated Annotation using Multiple IEA Methods findings: [] - id: PMID:16787417 title: 'GRK1 and GRK7: unique cellular distribution and widely different activities of opsin phosphorylation in the zebrafish rods and cones.' findings: - statement: Zebrafish has two GRK7 paralogs, GRK7-1 (grk7a) and GRK7-2 (grk7b). supporting_text: Screening of the ocular cDNAs identified two homologs for each of GRK1 (1A and 1B) and GRK7 (7-1 and 7-2), and they were classified into three GRK subfamilies, 1 A, 1B and 7 by phylogenetic analysis. - statement: Recombinant zebrafish GRKs phosphorylate light-activated rhodopsin; GRK7-1 has 32-fold higher Vmax than GRK1A. supporting_text: The recombinant GRKs phosphorylated light-activated rhodopsin, and the Vmax value of the major cone subtype, GRK7-1, was 32-fold higher than that of the rod kinase, GRK1A. - statement: GRK7-1 and GRK1B localise to cone outer segments (GRK7-2 localisation not stated in the abstract). supporting_text: In situ hybridization and immunohistochemical studies localized both GRK1B and GRK7-1 in the cone outer segments and GRK1A in the rod outer segments. full_text_unavailable: true reference_review: relevance: HIGH correctness: VERIFIED review_notes: Title matches the cached record (Wada et al. 2006, J Neurochem). Abstract only, but UniProt cites it (ECO:0000269) for both rhodopsin-kinase reactions of Q1XHL7; GRK7-2 in this paper is grk7b. Source of the IDA row. - id: file:DANRE/grk7b/grk7b-uniprot.txt title: UniProtKB entry Q1XHL7 for Danio rerio grk7b findings: - statement: Opsin kinase for photoresponse shutoff; expressed in eye, pineal and brain. record_section: ["CC:FUNCTION"] supporting_text: Retina-specific kinase involved in the shutoff of the photoresponse and adaptation to changing light conditions via cone opsin phosphorylation, including rhodopsin (RHO). reference_review: relevance: MEDIUM correctness: VERIFIED review_notes: |- UniProt Q1XHL7: FUNCTION and CATALYTIC ACTIVITY are experimentally sourced from PMID:16787417; SUBCELLULAR LOCATION is by similarity to carp GRK7 (Q8WMV0). - id: file:DANRE/grk7b/grk7b-deep-research-falcon.md title: Falcon deep research report on zebrafish grk7b (Q1XHL7) findings: - statement: 'grk7b is one of two zebrafish GRK7 paralogs (grk7a and grk7b), a cone/opsin kinase of the retinal GRK family. An anti-GRK7 antibody detects recombinant Grk7a and Grk7b but not Grk1, confirming grk7b is a bona fide GRK7-family opsin kinase rather than an unrelated protein with a similar symbol. ' supporting_text: Multiple zebrafish studies explicitly document that zebrafish possess **two GRK7 paralogs, grk7a and grk7b**, consistent with UniProt’s naming and with teleost genome duplication. - statement: 'GRK7 proteins are retinal opsin kinases that phosphorylate activated visual pigments (opsins) in photoreceptors to promote termination and recovery of phototransduction, with grk7b assigned a serine/threonine opsin-kinase molecular function acting on photoactivated cone opsins. ' supporting_text: GRK7 proteins are **retinal G protein–coupled receptor kinases** (“opsin kinases”) that act in photoreceptors by **phosphorylating activated visual pigments (opsins)** to promote termination/recovery of phototransduction. - statement: 'GRK7-family activity sits in the phototransduction recovery/termination module, upstream of return to baseline electrical state and completion of response recovery. ' supporting_text: GRK7-family activity sits in the **phototransduction recovery/termination module**, upstream of return to baseline electrical state and completion of response recovery. - statement: 'The strongest direct retinal evidence for grk7b is transcriptomic: in an adult zebrafish photoreceptor scRNA-seq atlas, grk7b is enriched in UV cones, supporting a UV-cone phototransduction role. ' supporting_text: A high-confidence, gene-specific finding is that **grk7b is enriched in adult UV cones**. - statement: 'Larval retinal GRK7 signal is dominated by grk7a, not grk7b; most direct loss-of-function cone-recovery phenotypes in larvae are attributed to grk7a, so strong larval phenotypes should not be assigned to grk7b without direct evidence. ' supporting_text: In larval zebrafish, multiple lines of evidence indicate **grk7a is the predominant cone-expressed GRK7 paralog during early development**, while grk7b expression is comparatively low in photoreceptors at these stages. - statement: 'grk7b transcripts are detected in zebrafish pineal tissue by in situ hybridization, but grk7b knockdown does not have a remarkable effect on parapinopsin photoproduct inactivation, suggesting grk7b is not the primary kinase in that pineal context. ' supporting_text: Functionally, however, for pineal parapinopsin photoproduct inactivation, **GRK7a** knockdown slows recovery while **GRK7b** knockdown does **not** show a remarkable effect, suggesting grk7b is not the primary kinase for that pineal assay context. - statement: 'GRK7-family kinase activity is modulated by cAMP/PKA-dependent phosphorylation; PKA phosphorylation inhibits rhodopsin kinase activity, proposed to downregulate GRKs in darkness when cAMP is elevated. ' supporting_text: GRK1 and GRK7 are **PKA-phosphorylated** and that phosphorylation **inhibits rhodopsin kinase activity**, proposed as a mechanism to downregulate GRKs in darkness when cAMP is elevated; it further notes paralog/cell-type specificity (e.g., zebrafish cones show cAMP downregulates GRK7 but not cone GRK1b). - statement: 'A key annotation caveat: many GRK7 biochemical and phosphorylation assays use antibodies that recognize both GRK7 paralogs, so they are largely paralog-nonresolving for grk7b specifically. ' supporting_text: Many biochemical and phosphorylation assays use antibodies that recognize **both GRK7 paralogs**, limiting paralog-resolved conclusions for phosphorylation state and abundance. reference_review: relevance: LOW correctness: VERIFIED review_notes: Deep-research summary used only to locate primary papers; its retinal-recovery statements concern grk7a. - id: PMID:33579376 title: Functional identification of an opsin kinase underlying inactivation of the pineal bistable opsin parapinopsin in zebrafish. reference_review: relevance: HIGH correctness: VERIFIED review_notes: |- Title matches the cached record (Kawano-Yamashita et al. 2021, Zoological Lett; full text cached). Only in vivo knockdown of grk7b: no remarkable effect on pineal parapinopsin inactivation, unlike grk7a. findings: - statement: grk7b knockdown does not remarkably affect parapinopsin photoproduct inactivation in the pineal; grk7a is the main kinase. supporting_text: We found that GRK7a knockdown slowed recovery of the response of parapinopsin photoreceptor cells, whereas GRK1b knockdown or GRK7b knockdown did not have a remarkable effect, suggesting that GRK7a, a cone-type GRK, is mainly responsible for inactivation of the parapinopsin photoproduct in zebrafish larvae. - statement: Adult pineal expresses GRK1b, GRK7a and GRK7b. supporting_text: |- The pineal organ in adult zebrafish was reported to express three types of GRKs: the cone-related GRKs GRK1b and GRK7a, as well as GRK7b, a paralog of GRK7a [29]. - id: PMID:16039565 title: Knockdown of cone-specific kinase GRK7 in larval zebrafish leads to impaired cone response recovery and delayed dark adaptation. reference_review: relevance: MEDIUM correctness: VERIFIED review_notes: Title matches the cached record (Rinner et al. 2005, Neuron). Abstract only. Cloned both grk7 orthologs but the knockdown phenotype (delayed cone recovery) is for grk7a, not grk7b. findings: - statement: grk7a knockdown delays cone photoresponse recovery and reduces temporal contrast sensitivity. supporting_text: Photoresponse recovery in Grk7a-deficient larvae was delayed in electroretinographic measurements, and temporal contrast sensitivity was reduced, particularly under bright-light conditions. - id: PMID:34462505 title: Partitioning of gene expression among zebrafish photoreceptor subtypes. reference_review: relevance: MEDIUM correctness: VERIFIED review_notes: |- Title matches the cached record (Ogawa & Corbo 2021, Sci Rep; full text cached). Transcriptomics: grk7b is enriched in UV cones while grk7a is in the other cone subtypes. findings: - statement: grk7b is differentially enriched in UV cones; grk7a in other cone types. supporting_text: Additionally, we found multiple pairs of paralogous genes that were differentially enriched between UV cones (grk7b, cngb3.2, and guca1e) and other cone types (grk7a, cngb3.1, and guca1e.2). - id: PMID:30372740 title: Grk1b and Grk7a Both Contribute to the Recovery of the Isolated Cone Photoresponse in Larval Zebrafish. reference_review: relevance: LOW correctness: VERIFIED review_notes: Title matches the cached record (Brockerhoff lab 2018, Invest Ophthalmol Vis Sci; full text cached). About grk1b/grk7a; used only to note that the anti-Grk7 antibody recognises both paralogs, so immunostaining does not distinguish Grk7b. findings: - statement: The anti-Grk7 antibody recognises both Grk7a and Grk7b. supporting_text: We generated a rabbit polyclonal antibody that recognizes both paralogs of zebrafish Grk7 (Grk7a and Grk7b). core_functions: - description: Grk7b (GRK7-2) is a membrane-anchored, UV-cone-enriched G protein-coupled receptor kinase that phosphorylates light-activated opsin, the first step in shutting off the opsin signal; demonstrated by recombinant-enzyme phosphorylation of light-activated rhodopsin, while its in vivo contribution relative to grk7a remains unresolved. molecular_function: id: GO:0050254 label: rhodopsin kinase activity directly_involved_in: - id: GO:0009966 label: regulation of signal transduction locations: - id: GO:0016020 label: membrane supported_by: - reference_id: PMID:16787417 supporting_text: The recombinant GRKs phosphorylated light-activated rhodopsin, and the Vmax value of the major cone subtype, GRK7-1, was 32-fold higher than that of the rod kinase, GRK1A. - reference_id: file:DANRE/grk7b/grk7b-uniprot.txt record_section: ["CC:FUNCTION"] supporting_text: Retina-specific kinase involved in the shutoff of the photoresponse and adaptation to changing light conditions via cone opsin phosphorylation, including rhodopsin (RHO). - reference_id: PMID:34462505 supporting_text: Additionally, we found multiple pairs of paralogous genes that were differentially enriched between UV cones (grk7b, cngb3.2, and guca1e) and other cone types (grk7a, cngb3.1, and guca1e.2). suggested_questions: - question: Does grk7b loss delay photoresponse recovery specifically in UV cones, where it is the enriched GRK7 paralog, or does grk7a compensate? - question: What are the kinetic parameters of recombinant Grk7b on UV opsin (opn1sw1) versus rhodopsin, and how do they compare with Grk7a? suggested_experiments: - description: Generate a grk7b CRISPR mutant and record UV-cone-isolated electroretinograms (and grk7a/grk7b double mutants) to test whether Grk7b contributes to cone response recovery in the UV cone subtype. hypothesis: Grk7b is required for rapid photoresponse shutoff in UV cones, a role masked in whole-retina recordings dominated by grk7a-expressing cones.