id: P09132
gene_symbol: SRP19
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: 'SRP19 is the 19 kDa protein subunit of the signal recognition particle (SRP), the cytosolic ribonucleoprotein that mediates co-translational targeting of secretory and membrane proteins to the endoplasmic reticulum (ER). SRP consists of a single 7SL RNA (~300 nucleotides) and six proteins (SRP9, SRP14, SRP19, SRP54, SRP68, SRP72). SRP19 binds directly to the SRP 7SL RNA and is the key assembly factor of the S domain: it is intrinsically disordered when free and folds upon RNA binding, clamping the apical tetraloops of helices 6 and 8 and thereby remodeling the asymmetric internal loop of helix 8 to create the binding site for the signal-sequence-recognition GTPase SRP54. SRP54 can only bind the SRP RNA after SRP19 has bound (ordered, SRP54-late assembly), so SRP19 is required for incorporation of SRP54 and for productive SRP assembly. SRP19 is an RNA-binding/scaffolding protein, not a GTPase. The mature particle functions in the cytoplasm, but SRP partially assembles in the nucleus/nucleolus, and SRP19 is actively imported into the nucleus by importin 8 and transportin.'
alternative_products:
- name: '1'
  id: P09132-1
- name: '2'
  id: P09132-2
  sequence_note: VSP_042540
- name: '3'
  id: P09132-3
  sequence_note: VSP_044524
existing_annotations:
- term:
    id: GO:0005786
    label: signal recognition particle, endoplasmic reticulum targeting
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: part_of
  review:
    summary: Phylogenetic annotation of SRP19 as a constitutive subunit of the signal recognition particle. Conserved and directly demonstrated.
    action: ACCEPT
    reason: Core cellular component; SRP19 is one of the six SRP protein subunits.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: 'consists of a 7SL RNA molecule of 300 nucleotides and 6 protein'
- term:
    id: GO:0008312
    label: 7S RNA binding
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: Phylogenetic annotation of SRP19's core molecular function, binding the SRP 7SL RNA. SRP19 binds directly to 7SL RNA and scaffolds S-domain assembly. Conserved across the SRP19 family.
    action: ACCEPT
    reason: Core molecular function; SRP19 binds the SRP 7SL RNA, supported by IDA.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: Binds directly to 7SL RNA
- term:
    id: GO:0006617
    label: SRP-dependent cotranslational protein targeting to membrane, signal sequence recognition
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: Phylogenetic annotation of SRP19's role in SRP-dependent co-translational targeting. SRP19 enables SRP54 incorporation, and SRP54 performs signal-sequence recognition; SRP19 is part of the complex performing this process.
    action: ACCEPT
    reason: Core biological process; SRP19 is required for assembly of the signal-sequence-recognizing SRP54 into SRP.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: Mediates
- term:
    id: GO:0005654
    label: nucleoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Electronic transfer of nucleoplasm localization. SRP19 is imported into the nucleus and SRP partially assembles in the nucleus/nucleolus; this is an assembly compartment, not the core ER-targeting site of action.
    action: KEEP_AS_NON_CORE
    reason: Real assembly-stage localization, but not the defining cytoplasmic ER-targeting site of action.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: 'Nucleus,'
- term:
    id: GO:0005730
    label: nucleolus
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Electronic transfer of nucleolar localization, where SRP partially assembles. An assembly compartment rather than the core ER-targeting site.
    action: KEEP_AS_NON_CORE
    reason: Real assembly-stage localization, secondary to the cytoplasmic site of SRP function.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: 'Nucleus, nucleolus'
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Electronic transfer of the cytoplasmic localization, the site where mature SRP functions in ER targeting. Consistent with experimental EXP evidence.
    action: ACCEPT
    reason: Correct core compartment; SRP acts in the cytoplasm.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm'
- term:
    id: GO:0006614
    label: SRP-dependent cotranslational protein targeting to membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: involved_in
  review:
    summary: InterPro-based electronic assignment of the core SRP-dependent co-translational targeting process.
    action: ACCEPT
    reason: Correct core process; redundant with IBA/TAS evidence.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: mediates the cotranslational targeting
- term:
    id: GO:0008312
    label: 7S RNA binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: InterPro-based annotation of SRP RNA (7S/7SL) binding, SRP19's core molecular function.
    action: ACCEPT
    reason: Correct core molecular function; redundant with IDA evidence.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: Binds directly to 7SL RNA
- term:
    id: GO:0048500
    label: signal recognition particle
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: part_of
  review:
    summary: InterPro-based annotation of SRP complex membership (general SRP term).
    action: ACCEPT
    reason: Core cellular component; redundant with the more specific GO:0005786.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: 'Component of the signal recognition particle (SRP) complex'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:33961781
  qualifier: enables
  review:
    summary: Proteome-scale interactome capturing the SRP19-SRP68 (Q9UHB9) interaction within the SRP S domain. Biologically meaningful but the bare protein binding term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: Records the real SRP68 interaction, but bare protein binding is uninformative; covered by SRP complex membership and 7S RNA binding.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: 'P09132; Q9UHB9: SRP68'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:35271311
  qualifier: enables
  review:
    summary: OpenCell endogenous-tagging interactome capturing the SRP19-SRP68 (Q9UHB9) interaction. Bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: Records the real SRP68 interaction; bare protein binding is uninformative.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: 'P09132; Q9UHB9: SRP68'
- term:
    id: GO:0005786
    label: signal recognition particle, endoplasmic reticulum targeting
  evidence_type: NAS
  original_reference_id: PMID:34208095
  qualifier: part_of
  review:
    summary: ComplexPortal NAS assertion of SRP complex membership from the SRP review, which notes SRP19 functions to stabilize the 7SL structure.
    action: ACCEPT
    reason: Core cellular component; SRP19 is an SRP subunit.
    supported_by:
    - reference_id: PMID:34208095
      supporting_text: SRP19 functions to stabilize the 7SL structure
- term:
    id: GO:0006617
    label: SRP-dependent cotranslational protein targeting to membrane, signal sequence recognition
  evidence_type: NAS
  original_reference_id: PMID:34208095
  qualifier: involved_in
  review:
    summary: ComplexPortal NAS annotation of SRP19's role in the signal-sequence-recognition step. SRP19 enables SRP54 incorporation; signal-sequence recognition is performed by SRP54 within the SRP of which SRP19 is part.
    action: ACCEPT
    reason: Core biological process at the complex level; SRP19 is required for assembly of the signal-sequence-recognizing SRP54.
    supported_by:
    - reference_id: PMID:34208095
      supporting_text: SRP19 functions to stabilize the 7SL structure
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: IDA
  original_reference_id: GO_REF:0000052
  qualifier: located_in
  review:
    summary: HPA immunofluorescence cytosolic localization, consistent with the cytoplasmic site of SRP function.
    action: ACCEPT
    reason: Correct core compartment; SRP acts in the cytosol.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm'
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-1799332
  qualifier: located_in
  review:
    summary: Reactome curation of cytosolic localization, consistent with SRP's cytoplasmic site of action.
    action: ACCEPT
    reason: Correct compartment; redundant with HPA/UniProt evidence.
    supported_by:
    - reference_id: file:human/SRP19/SRP19-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm'
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: EXP
  original_reference_id: PMID:10618370
  qualifier: located_in
  review:
    summary: Direct experimental cytoplasmic localization of SRP19, alongside its nucleolar localization during SRP assembly.
    action: ACCEPT
    reason: Correct core compartment; experimentally demonstrated.
    supported_by:
    - reference_id: PMID:10618370
      supporting_text: prominent nucleolar localization
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: EXP
  original_reference_id: PMID:11682607
  qualifier: located_in
  review:
    summary: Direct experimental cytoplasmic localization of SRP19 from the nuclear-import study, which also documents nuclear/nucleolar pools.
    action: ACCEPT
    reason: Correct core compartment; experimentally demonstrated.
    supported_by:
    - reference_id: PMID:11682607
      supporting_text: imported into the nucleus
- term:
    id: GO:0003723
    label: RNA binding
  evidence_type: IPI
  original_reference_id: PMID:17434535
  qualifier: enables
  review:
    summary: SRP19 binds the SRP RNA; RNA binding is the general parent of the more specific 7S RNA binding. This DisProt annotation reflects SRP19's disorder-to-order RNA-binding transition.
    action: ACCEPT
    reason: Correct molecular function; the more specific GO:0008312 (7S RNA binding) better captures SRP19's role.
    supported_by:
    - reference_id: PMID:17434535
      supporting_text: SRP19 protein is unstructured
- term:
    id: GO:0008312
    label: 7S RNA binding
  evidence_type: IDA
  original_reference_id: PMID:27899666
  qualifier: enables
  review:
    summary: Direct structural evidence that SRP19 is a scaffolding protein clamping helices 6 and 8 of SRP RNA, preparing helix 8 for SRP54 binding. Core SRP RNA-binding molecular function.
    action: ACCEPT
    reason: Core molecular function with direct structural (IDA) support.
    supported_by:
    - reference_id: PMID:27899666
      supporting_text: SRP19 is a scaffolding protein clamping helices 6 and 8 of SRP RNA
- term:
    id: GO:0043022
    label: ribosome binding
  evidence_type: IDA
  original_reference_id: PMID:27899666
  qualifier: contributes_to
  review:
    summary: SRP19 contributes to the SRP complex's ribosome interaction; the study concerns SRP RNA remodeling and ribosome binding, in which SRP19 clamps the RNA. The contributes_to qualifier appropriately reflects that ribosome binding is a complex-level activity.
    action: KEEP_AS_NON_CORE
    reason: Complex-level activity to which SRP19 contributes (contributes_to); SRP19's defining MF is SRP RNA binding.
    supported_by:
    - reference_id: PMID:27899666
      supporting_text: 5f-loop involved in ribosome binding
- term:
    id: GO:0048500
    label: signal recognition particle
  evidence_type: IDA
  original_reference_id: PMID:27899666
  qualifier: part_of
  review:
    summary: Direct structural evidence placing SRP19 within the SRP complex.
    action: ACCEPT
    reason: Core cellular component; structurally demonstrated.
    supported_by:
    - reference_id: PMID:27899666
      supporting_text: SRP19 is a scaffolding protein clamping helices 6 and 8 of SRP RNA
- term:
    id: GO:0003723
    label: RNA binding
  evidence_type: HDA
  original_reference_id: PMID:22658674
  qualifier: enables
  review:
    summary: High-throughput mRNA-interactome capture detecting SRP19 as an RNA-binding protein. Correct but generic parent of 7S RNA binding.
    action: ACCEPT
    reason: Correct general molecular function; the specific GO:0008312 better captures SRP19's SRP RNA binding.
    supported_by:
    - reference_id: PMID:22658674
      supporting_text: Insights into RNA biology from an atlas of mammalian mRNA-binding proteins
- term:
    id: GO:0005786
    label: signal recognition particle, endoplasmic reticulum targeting
  evidence_type: IDA
  original_reference_id: PMID:18089836
  qualifier: part_of
  review:
    summary: Drug-target screen identifying SRP as the target of TAS-103; the compound disrupts SRP complex formation and reduces SRP14 and SRP19, detecting SRP19 as part of the SRP complex.
    action: ACCEPT
    reason: Core cellular component; SRP19 is detected as part of the SRP complex.
    supported_by:
    - reference_id: PMID:18089836
      supporting_text: disrupts SRP complex formation
- term:
    id: GO:0008312
    label: 7S RNA binding
  evidence_type: IDA
  original_reference_id: PMID:17434535
  qualifier: enables
  review:
    summary: Direct evidence that SRP19 folds upon binding SRP RNA, forming a threefold RNA-protein interface that gates SRP54 binding. Core SRP RNA-binding molecular function.
    action: ACCEPT
    reason: Core molecular function with direct (IDA) support.
    supported_by:
    - reference_id: PMID:17434535
      supporting_text: SRP19 protein is unstructured
- term:
    id: GO:0005730
    label: nucleolus
  evidence_type: IDA
  original_reference_id: PMID:10618370
  qualifier: located_in
  review:
    summary: Direct evidence that GFP-SRP19 displays prominent nucleolar localization, reflecting the nuclear/nucleolar stage of SRP assembly. An assembly compartment rather than the core ER-targeting site.
    action: KEEP_AS_NON_CORE
    reason: Real assembly-stage localization; not the defining cytoplasmic site of SRP function.
    supported_by:
    - reference_id: PMID:10618370
      supporting_text: prominent nucleolar localization
- term:
    id: GO:0005786
    label: signal recognition particle, endoplasmic reticulum targeting
  evidence_type: TAS
  original_reference_id: PMID:1678319
  qualifier: part_of
  review:
    summary: TAS annotation of SRP membership from the positional-cloning paper that mapped SRP19 near the APC locus and found one gene identical to SRP19, the 19 kDa SRP component.
    action: ACCEPT
    reason: Core cellular component; SRP19 is an SRP subunit. The cited paper correctly identifies SRP19 as the SRP 19 kDa component.
    supported_by:
    - reference_id: PMID:1678319
      supporting_text: identical to SRP19
- term:
    id: GO:0006613
    label: cotranslational protein targeting to membrane
  evidence_type: TAS
  original_reference_id: PMID:1678319
  qualifier: involved_in
  review:
    summary: TAS annotation of the (older parent) co-translational protein targeting process for SRP19 as an SRP component.
    action: ACCEPT
    reason: Correct biological process; the SRP-dependent child terms better specify SRP19's role.
    supported_by:
    - reference_id: PMID:1678319
      supporting_text: identical to SRP19
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  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
  findings: []
- id: GO_REF:0000052
  title: Gene Ontology annotation based on curation of immunofluorescence data
  findings: []
- id: PMID:10618370
  title: Signal recognition particle components in the nucleolus.
  findings:
  - statement: SRP19 binds SRP RNA independently and must bind before SRP54, effecting a conformational change promoting SRP54 binding; GFP-SRP19 shows prominent nucleolar plus cytoplasmic localization.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Establishes ordered SRP assembly (SRP19 before SRP54) and the nucleolar assembly compartment.
- id: PMID:11682607
  title: Signal recognition particle protein 19 is imported into the nucleus by importin 8 (RanBP8) and transportin.
  findings:
  - statement: SRP19 is efficiently imported into the nucleus by importin 8 and transportin; a significant endogenous pool is nuclear/nucleolar.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Source of nuclear-import and nuclear/nucleolar localization annotations.
- id: PMID:1678319
  title: Identification of deletion mutations and three new genes at the familial polyposis locus.
  findings:
  - statement: Positional cloning at the APC/polyposis locus identified a gene identical to SRP19, the 19 kDa component of the ribosomal signal recognition particle.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Original mapping of SRP19; correctly identifies it as the SRP 19 kDa component despite the paper's APC focus.
- id: PMID:17434535
  title: A threefold RNA-protein interface in the signal recognition particle gates native complex assembly.
  findings:
  - statement: SRP19 is unstructured when free and folds into a compact core plus two extended RNA-binding loops upon binding SRP RNA; SRP54 subsequently binds the assembled SRP19-RNA complex.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Establishes SRP19's disorder-to-order RNA-binding transition gating SRP54 incorporation.
- id: PMID:18089836
  title: 'A new mechanism of 6-((2-(dimethylamino)ethyl)amino)-3-hydroxy-7H-indeno(2,1-c)quinolin-7-one dihydrochloride (TAS-103) action discovered by target screening with drug-immobilized affinity beads.'
  findings:
  - statement: SRP is the target of TAS-103; the compound disrupts SRP complex formation and reduces the amount of SRP14 and SRP19, detecting SRP19 within the SRP complex.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Detects SRP19 as part of the SRP complex; supports SRP membership.
- id: PMID:22658674
  title: Insights into RNA biology from an atlas of mammalian mRNA-binding proteins.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: High-throughput RNA-interactome capture; source of the generic RNA binding HDA annotation.
- id: PMID:27899666
  title: Structures of human SRP72 complexes provide insights into SRP RNA remodeling and ribosome interaction.
  findings:
  - statement: SRP19 is a scaffolding protein clamping helices 6 and 8 of SRP RNA, preparing the asymmetric loop of helix 8 for SRP54 binding; SRP72-RBD remodels the 5f-loop involved in ribosome binding.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Structural study establishing SRP19's RNA-clamping/scaffolding role and complex-level ribosome interaction.
- id: PMID:33961781
  title: Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Captures the SRP19-SRP68 interaction; bare protein binding term.
- id: PMID:34208095
  title: 'SRPassing Co-translational Targeting: The Role of the Signal Recognition Particle in Protein Targeting and mRNA Protection.'
  findings:
  - statement: SRP19 functions to stabilize the 7SL RNA structure within SRP; SRP consists of Alu and S domains with six proteins and 7SL RNA.
    reference_section_type: OTHER
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Authoritative SRP review; full text available. Used by ComplexPortal for NAS annotations.
- id: PMID:35271311
  title: 'OpenCell: Endogenous tagging for the cartography of human cellular organization.'
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Endogenous-tagging interactome; captures SRP19-SRP68 interaction, bare protein binding.
- id: Reactome:R-HSA-1799332
  title: 'Reactome: Nascent polypeptide:mRNA:ribosome complex binds signal recognition particle (SRP)'
  findings: []
- id: PMID:12086622
  title: Crystal structure of SRP19 in complex with the S domain of SRP RNA and its implication for the assembly of the signal recognition particle.
  findings:
  - statement: Crystal structure of SRP19 bound to the S-domain of SRP RNA shows SRP19 clamps the tetraloops of helices 6 and 8 (helix 6 acting as a splint), pre-organizing the SRP54-binding site on helix 8; unlike bacterial systems, human SRP54 cannot bind SRP RNA before SRP19, establishing SRP19 as an upstream eukaryotic assembly factor.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified (Oubridge et al., Mol Cell 2002). Foundational structural basis for SRP19's helix-6/8 RNA clamp and SRP54-late ordered assembly.
- id: PMID:38858088
  title: The nucleolar phase of signal recognition particle assembly.
  findings:
  - statement: GFP-SRP19 accumulates in nucleoli and co-localizes with nucleolar markers; nucleolar disruption (low-dose actinomycin D, uL18/RPL5 depletion) relocalizes SRP19, and SRP proteins associate with many nucleolar/ribosome-biogenesis factors, supporting a bona fide nucleolar phase of SRP assembly.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: PubMed-verified (Issa et al., Life Sci Alliance 2024). Strengthens the nucleolar SRP-assembly compartment for SRP19 (a non-core, assembly-stage localization).
- id: PMID:35754847
  title: Signal Recognition Particle in Human Diseases.
  findings:
  - statement: Reviews SRP-related human disease; SRP19 is among the SRP autoantigens (anti-SRP19, anti-SRP54, anti-SRP72, anti-7SL) recognized in immune-mediated necrotizing myopathy (IMNM)/anti-SRP myositis.
    reference_section_type: OTHER
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: PubMed-verified (Kellogg et al., Front Genet 2022). Disease/autoantigen context for SRP19; not a core molecular-function source.
- id: file:human/SRP19/SRP19-uniprot.txt
  title: UniProt entry P09132 (SRP19_HUMAN), Signal recognition particle 19 kDa protein
  findings:
  - statement: SRP19 is a subunit of the SRP ribonucleoprotein (7SL RNA + six proteins); binds directly to 7SL RNA and mediates binding of SRP54 to the SRP complex; cytoplasmic with nuclear/nucleolar assembly pools.
    reference_section_type: OTHER
core_functions:
- description: SRP RNA-binding scaffolding subunit that binds the SRP 7SL RNA, clamping helices 6 and 8 and remodeling helix 8 to create the SRP54 binding site, thereby enabling ordered assembly of the SRP S domain.
  molecular_function:
    id: GO:0008312
    label: 7S RNA binding
  in_complex:
    id: GO:0005786
    label: signal recognition particle, endoplasmic reticulum targeting
  supported_by:
  - reference_id: PMID:27899666
    supporting_text: SRP19 is a scaffolding protein clamping helices 6 and 8 of SRP RNA
  - reference_id: PMID:12086622
    supporting_text: >-
      SRP19 clamps the tetraloops of two branched helices (helices 6 and 8) and allows them to
      interact side by side.
  - reference_id: file:human/SRP19/SRP19-uniprot.txt
    supporting_text: Binds directly to 7SL RNA
  directly_involved_in:
  - id: GO:0006617
    label: SRP-dependent cotranslational protein targeting to membrane, signal sequence recognition
- description: Required assembly factor for incorporation of the signal-sequence-recognition GTPase SRP54 into the SRP, gating productive SRP assembly for co-translational ER targeting.
  molecular_function:
    id: GO:0008312
    label: 7S RNA binding
  in_complex:
    id: GO:0048500
    label: signal recognition particle
  supported_by:
  - reference_id: file:human/SRP19/SRP19-uniprot.txt
    supporting_text: Mediates
  - reference_id: PMID:17434535
    supporting_text: SRP19 protein is unstructured
  - reference_id: PMID:12086622
    supporting_text: >-
      In Archaea and Eukarya, SRP19 binds to 7SL RNA and promotes the incorporation of SRP54,
      which contains the binding sites for GTP, the signal peptide, and the membrane-bound SRP
      receptor.
  directly_involved_in:
  - id: GO:0006614
    label: SRP-dependent cotranslational protein targeting to membrane
proposed_new_terms: []
suggested_questions:
- question: What is the functional significance of the nuclear/nucleolar SRP19 pool and its active import, given that mature SRP acts in the cytoplasm?
- question: Do the alternative SRP19 isoforms differ in RNA-binding or SRP54-recruitment activity?
suggested_experiments:
- description: Reconstitute SRP assembly with wild-type versus RNA-clamp-deficient SRP19 mutants to quantify the requirement for SRP19 in SRP54 incorporation and signal-sequence-dependent targeting.
- description: Track SRP19 nucleocytoplasmic shuttling and SRP assembly state in cells with impaired importin-8/transportin import to test whether nuclear assembly contributes to functional SRP biogenesis.