FKBP42/TWISTED DWARF1 is a membrane-associated immunophilin-like regulator of selected ABC transporters. It binds ABCB1 and ABCB19, promotes their plasma-membrane localization and auxin transport, and works with HSP90 in transporter maturation and stability. A separate TPR-mediated interaction with vacuolar ABCC transporters modulates conjugate uptake. TWD1 has experimentally demonstrated antiaggregation activity and calmodulin binding and occurs at the plasma membrane, endoplasmic reticulum and tonoplast. Its transport-regulatory functions influence organ and cell elongation, leaf shape, stamen growth and pollen development. Calmodulin-dependent prolyl isomerase activity has recently been reported for its isolated FKBP domain in a preprint; activity of intact native TWD1 and direct isomerization of an ABCB peptide bond remain unresolved.
Definition: Binding to non-native proteins to suppress their aggregation, without necessarily catalyzing productive refolding.
Justification: TWD1 directly suppresses thermal aggregation of citrate synthase. The assay establishes holdase activity and should not be treated as autonomous productive folding.
Supporting Evidence:
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003755 peptidyl-prolyl cis-trans isomerase activity | IDA NOT PMID:12410806 Characterization of Arabidopsis thaliana AtFKBP42 that is me... | UNDECIDED | Summary: The unconditional absence of TWD1 PPIase activity is unresolved in light of new domain-level evidence. Reason: This row is negated and asserts absence, not presence. The historical negative assays and the 2025 synthesis support failure to detect activity under the tested conditions. The July2026 preprint instead reports CaM-dependent tetrapeptide isomerization for recombinant FKBD1β180, inhibited by FK506/rapamycin and retained with EGTA. Its Figure5 does not establish catalysis by intact membrane-anchored TWD1, and Results versus Methods name AFPF versus ALPF substrates. These limits leave the general negative claim unresolved. No contextual extension is present, so prose cannot convert this NOT into a conditional assertion or justify accepting both signs. Supporting Evidence: PMID:41027915 all attempts to validate a PPIase activity on TWD1 have failed url:https://www.biorxiv.org/content/10.64898/2026.07.24.740493v2.full Next, we measured the PPIase activity of recombinant FKBD (TWD11-180) protein url:https://www.biorxiv.org/content/10.64898/2026.07.24.740493v2.full TWD1 PPIase activation by calmodulin was not dependent on Ca2+ |
| GO:0003755 peptidyl-prolyl cis-trans isomerase activity | ISS PMID:12410806 Characterization of Arabidopsis thaliana AtFKBP42 that is me... | UNDECIDED | Summary: A general PPIase assignment to intact TWD1 is not settled by family similarity or the recent isolated-domain assay. Reason: The original ISS inference conflicts with the historical negative target assays. The new preprint supplies genuine positive catalytic evidence for the CaM-bound FKBD1β180 construct, not simply family membership, but intact native activity and an ABCB1 peptide-bond substrate are not directly demonstrated. The Results/Methods tetrapeptide discrepancy and preliminary status warrant a bounded unresolved judgment for this general full-product claim, consistent with the unresolved NOT row. Supporting Evidence: PMID:41027915 all attempts to validate a PPIase activity on TWD1 have failed url:https://www.biorxiv.org/content/10.64898/2026.07.24.740493v2.full Next, we measured the PPIase activity of recombinant FKBD (TWD11-180) protein url:https://www.biorxiv.org/content/10.64898/2026.07.24.740493v2.full TWD1 PPIase activation by calmodulin was not dependent on Ca2+ |
| GO:0005515 protein binding | IPI PMID:14517332 TWISTED DWARF1, a unique plasma membrane-anchored immunophil... | MODIFY | Summary: TWD1 binds and activates the auxin transporter ABCB1. Reason: The original physical interaction is functionally resolved by target coexpression, transport assays and DEP-motif mutagenesis. Transporter activator activity captures a measured role beyond bare binding; it does not assert that the proposed prolyl-isomerization mechanism has been directly demonstrated on ABCB1. Proposed replacements: transporter activator activity Supporting Evidence: PMID:32699109 The D/E-P1008 motif is also important for ABCB1-TWD1 interactions and activation of ABCB1-mediated auxin transport by TWD1. |
| GO:0005515 protein binding | IPI PMID:15133126 Arabidopsis immunophilin-like TWD1 functionally interacts wi... | MODIFY | Summary: TWD1 binds a vacuolar ABCC transporter and modulates conjugate transport. Reason: PMID15133126 maps ABCC1/AtMRP1 binding to the TPR region, verifies a native complex, and measures substrate-dependent effects of recombinant TWD1 on uptake into isolated vacuoles. Because these vacuoles contain multiple ABCCs and the effect differs by substrate, use transporter regulator activity rather than an unconditional ABCC1 activation claim or transporter catalysis by TWD1. Proposed replacements: transporter regulator activity Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ AtMRP1 interacted with the C-terminal stretch comprising the TPR domain but not with the N-terminus containing the PPIase-like domain url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ TWD1-3 protein stimulated the uptake of 17Ξ²-estradiol 17-(Ξ²-d-glucuronide) |
| GO:0005516 calmodulin binding | IDA PMID:12410806 Characterization of Arabidopsis thaliana AtFKBP42 that is me... | ACCEPT | Summary: TWD1 directly binds calmodulin. Reason: The original recombinant cross-linking and newer CaM-affinity experiments independently establish binding. The fragment-specific calcium dependence in the preprint should not be generalized to all TWD1βCaM interactions, nor does binding alone settle intact-protein PPIase activity. Supporting Evidence: PMID:12410806 can be cross-linked to calmodulin url:https://www.biorxiv.org/content/10.64898/2026.07.24.740493v2.full The FKBD (aa 1-180) and full-length TWD1 minus membrane anchor (aa 1-339) bind to CaM-sepharose. |
| GO:0005774 vacuolar membrane | EXP PMID:12410806 Characterization of Arabidopsis thaliana AtFKBP42 that is me... | ACCEPT | Summary: A tonoplast-associated TWD1 pool is supported by biochemical localization and transporter complexes. Reason: The full 2004 primary corroborates the earlier immunolocalization using sucrose-gradient fractions and native ABCC1 complexes. This location coexists with plasma-membrane and ER pools; neither one excludes the others. The overexpressed HA-tagged localization assay is distinguished from native-complex recovery. Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ TWD1-HA-positive fractions overlap to similar extends with both plasma membrane (40 and 50% sucrose) and vacuolar fractions (30 and 40% sucrose url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ AtMRP1 interacted with the C-terminal stretch comprising the TPR domain but not with the N-terminus containing the PPIase-like domain |
| GO:0005774 vacuolar membrane | EXP PMID:15133126 Arabidopsis immunophilin-like TWD1 functionally interacts wi... | ACCEPT | Summary: A tonoplast-associated TWD1 pool is supported by biochemical localization and transporter complexes. Reason: The full 2004 primary corroborates the earlier immunolocalization using sucrose-gradient fractions and native ABCC1 complexes. This location coexists with plasma-membrane and ER pools; neither one excludes the others. The overexpressed HA-tagged localization assay is distinguished from native-complex recovery. Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ TWD1-HA-positive fractions overlap to similar extends with both plasma membrane (40 and 50% sucrose) and vacuolar fractions (30 and 40% sucrose url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ AtMRP1 interacted with the C-terminal stretch comprising the TPR domain but not with the N-terminus containing the PPIase-like domain |
| GO:0005774 vacuolar membrane | IEA GO_REF:0000044 | ACCEPT | Summary: A tonoplast-associated TWD1 pool is supported by biochemical localization and transporter complexes. Reason: The full 2004 primary corroborates the earlier immunolocalization using sucrose-gradient fractions and native ABCC1 complexes. This location coexists with plasma-membrane and ER pools; neither one excludes the others. The overexpressed HA-tagged localization assay is distinguished from native-complex recovery. Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ TWD1-HA-positive fractions overlap to similar extends with both plasma membrane (40 and 50% sucrose) and vacuolar fractions (30 and 40% sucrose url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ AtMRP1 interacted with the C-terminal stretch comprising the TPR domain but not with the N-terminus containing the PPIase-like domain |
| GO:0005783 endoplasmic reticulum | EXP PMID:20971896 The ER-localized TWD1 immunophilin is necessary for localiza... | ACCEPT | Summary: TWD1 has an experimentally supported endoplasmic-reticulum location. Reason: The native-promoter tagged-protein root study resolves ER localization and links loss of TWD1 to ABCB retention during biogenesis. Retain the informative root organelle claim alongside supported PM and tonoplast locations, without narrowing it to a particular ER subdomain. Supporting Evidence: PMID:20971896 confocal microscopy of fluorescently tagged TWD1 shows it to reside at the endoplasmic reticulum (ER). |
| GO:0005783 endoplasmic reticulum | IEA GO_REF:0000044 | ACCEPT | Summary: TWD1 has an experimentally supported endoplasmic-reticulum location. Reason: The native-promoter tagged-protein root study resolves ER localization and links loss of TWD1 to ABCB retention during biogenesis. Retain the informative root organelle claim alongside supported PM and tonoplast locations, without narrowing it to a particular ER subdomain. Supporting Evidence: PMID:20971896 confocal microscopy of fluorescently tagged TWD1 shows it to reside at the endoplasmic reticulum (ER). |
| GO:0005886 plasma membrane | EXP PMID:14517332 TWISTED DWARF1, a unique plasma membrane-anchored immunophil... | ACCEPT | Summary: TWD1 acts at the plasma membrane in documented tissues. Reason: Independent membrane fractionation, tagged-protein localization and the stamen endothecium/middle-layer imaging corroborate this location. PM localization is tissue- and developmental-context dependent and is compatible with the ER and tonoplast pools; the AtSubP prediction is supported independently. Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ TWD1-HA-positive fractions overlap to similar extends with both plasma membrane (40 and 50% sucrose) and vacuolar fractions (30 and 40% sucrose url:https://oup.silverchair-cdn.com/article-minimal/6581225 both TWD1βCFP and ABCB1βGFP localized on the endothecium and middle layer plasma membrane |
| GO:0005886 plasma membrane | EXP PMID:15133126 Arabidopsis immunophilin-like TWD1 functionally interacts wi... | ACCEPT | Summary: TWD1 acts at the plasma membrane in documented tissues. Reason: Independent membrane fractionation, tagged-protein localization and the stamen endothecium/middle-layer imaging corroborate this location. PM localization is tissue- and developmental-context dependent and is compatible with the ER and tonoplast pools; the AtSubP prediction is supported independently. Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ TWD1-HA-positive fractions overlap to similar extends with both plasma membrane (40 and 50% sucrose) and vacuolar fractions (30 and 40% sucrose url:https://oup.silverchair-cdn.com/article-minimal/6581225 both TWD1βCFP and ABCB1βGFP localized on the endothecium and middle layer plasma membrane |
| GO:0005886 plasma membrane | IDA PMID:12410806 Characterization of Arabidopsis thaliana AtFKBP42 that is me... | ACCEPT | Summary: TWD1 acts at the plasma membrane in documented tissues. Reason: Independent membrane fractionation, tagged-protein localization and the stamen endothecium/middle-layer imaging corroborate this location. PM localization is tissue- and developmental-context dependent and is compatible with the ER and tonoplast pools; the AtSubP prediction is supported independently. Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ TWD1-HA-positive fractions overlap to similar extends with both plasma membrane (40 and 50% sucrose) and vacuolar fractions (30 and 40% sucrose url:https://oup.silverchair-cdn.com/article-minimal/6581225 both TWD1βCFP and ABCB1βGFP localized on the endothecium and middle layer plasma membrane |
| GO:0005886 plasma membrane | IDA PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | ACCEPT | Summary: TWD1 acts at the plasma membrane in documented tissues. Reason: Independent membrane fractionation, tagged-protein localization and the stamen endothecium/middle-layer imaging corroborate this location. PM localization is tissue- and developmental-context dependent and is compatible with the ER and tonoplast pools; the AtSubP prediction is supported independently. Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ TWD1-HA-positive fractions overlap to similar extends with both plasma membrane (40 and 50% sucrose) and vacuolar fractions (30 and 40% sucrose url:https://oup.silverchair-cdn.com/article-minimal/6581225 both TWD1βCFP and ABCB1βGFP localized on the endothecium and middle layer plasma membrane |
| GO:0005886 plasma membrane | IEA GO_REF:0000044 | ACCEPT | Summary: TWD1 acts at the plasma membrane in documented tissues. Reason: Independent membrane fractionation, tagged-protein localization and the stamen endothecium/middle-layer imaging corroborate this location. PM localization is tissue- and developmental-context dependent and is compatible with the ER and tonoplast pools; the AtSubP prediction is supported independently. Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ TWD1-HA-positive fractions overlap to similar extends with both plasma membrane (40 and 50% sucrose) and vacuolar fractions (30 and 40% sucrose url:https://oup.silverchair-cdn.com/article-minimal/6581225 both TWD1βCFP and ABCB1βGFP localized on the endothecium and middle layer plasma membrane |
| GO:0005886 plasma membrane | ISM GO_REF:0000122 | ACCEPT | Summary: TWD1 acts at the plasma membrane in documented tissues. Reason: Independent membrane fractionation, tagged-protein localization and the stamen endothecium/middle-layer imaging corroborate this location. PM localization is tissue- and developmental-context dependent and is compatible with the ER and tonoplast pools; the AtSubP prediction is supported independently. Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC452592/ TWD1-HA-positive fractions overlap to similar extends with both plasma membrane (40 and 50% sucrose) and vacuolar fractions (30 and 40% sucrose url:https://oup.silverchair-cdn.com/article-minimal/6581225 both TWD1βCFP and ABCB1βGFP localized on the endothecium and middle layer plasma membrane |
| GO:0006457 protein folding | IMP PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | ACCEPT | Summary: TWD1 contributes a cochaperone and antiaggregation function to ABCB maturation. Reason: The stamen paper infers chaperoning from ABCB abundance/localization, not a direct refolding assay. Independent citrate-synthase antiaggregation and HSP90/client-interaction evidence support a contribution to protein folding and maturation. This process-level participation does not establish autonomous refolding catalysis or a native PPIase mechanism. Supporting Evidence: PMID:12410806 Recombinant AtFKBP42 prevents aggregation of citrate synthase in almost equimolar concentrations PMID:41027915 serving as a co-chaperone of this ABC-FKBP-HSP90 dynamic module. PMID:20971896 confocal microscopy of fluorescently tagged TWD1 shows it to reside at the endoplasmic reticulum (ER). |
| GO:0009555 pollen development | IMP PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | KEEP AS NON CORE | Summary: TWD1 supports pollen maturation and male-gametophyte development through local hormone transport. Reason: Direct pollen counts, viability staining and abnormal nuclear morphology in twd1 support this reproductive role. TWD1 supplies transporter regulation in the relevant tissues; the experiments do not make it a pollen mitosis enzyme or establish cell autonomy in the gametophyte. Supporting Evidence: url:https://oup.silverchair-cdn.com/article-minimal/6581225 both pollen viability and pollen number were significantly reduced in the tw1 and the abcb1abcb19 double mutant url:https://oup.silverchair-cdn.com/article-minimal/6581225 DAPI staining revealed pollen that were aborted, misshapen, and with multiple nuclei in twd1 and abcb1 abcb19 |
| GO:0010928 regulation of auxin mediated signaling pathway | IMP PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | KEEP AS NON CORE | Summary: TWD1 modifies auxin signaling outputs through transporter-dependent hormone distribution. Reason: The full stamen study measures local auxin-response reporters and altered flow in twd1. This is regulation of signaling through hormone availability, not direct participation in the nuclear auxin receptor machinery or proof that every affected tissue depends on ABCB1/19. Supporting Evidence: url:https://oup.silverchair-cdn.com/article-minimal/6581225 TWD1 mutation results in a reduced auxin flow in stamen filaments |
| GO:0044183 protein folding chaperone | IMP PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | MODIFY | Summary: The directly demonstrated intrinsic chaperone activity is antiaggregation holdase activity. Reason: Citrate-synthase aggregation suppression establishes substrate protection, while ABCB localization and HSP90 cooperation support a cochaperone role. None of these measures by itself demonstrates autonomous productive refolding by TWD1. Use a proposed holdase activity rather than silently equating trafficking rescue with direct protein-folding catalysis. Proposed replacements: protein holdase activity Supporting Evidence: PMID:12410806 Recombinant AtFKBP42 prevents aggregation of citrate synthase in almost equimolar concentrations PMID:41027915 serving as a co-chaperone of this ABC-FKBP-HSP90 dynamic module. |
| GO:0048229 gametophyte development | IMP PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | KEEP AS NON CORE | Summary: TWD1 supports pollen maturation and male-gametophyte development through local hormone transport. Reason: Direct pollen counts, viability staining and abnormal nuclear morphology in twd1 support this reproductive role. TWD1 supplies transporter regulation in the relevant tissues; the experiments do not make it a pollen mitosis enzyme or establish cell autonomy in the gametophyte. Supporting Evidence: url:https://oup.silverchair-cdn.com/article-minimal/6581225 both pollen viability and pollen number were significantly reduced in the tw1 and the abcb1abcb19 double mutant url:https://oup.silverchair-cdn.com/article-minimal/6581225 DAPI staining revealed pollen that were aborted, misshapen, and with multiple nuclei in twd1 and abcb1 abcb19 |
| GO:0048366 leaf development | IMP PMID:12410806 Characterization of Arabidopsis thaliana AtFKBP42 that is me... | KEEP AS NON CORE | Summary: TWD1 contributes to leaf expansion and shape. Reason: Although the original 2002 cache is incomplete, the independently recovered 2003 primary Figure1D directly compares twd1 leaf expansion and epinastic growth. This corroborates the existing developmental claim without assigning TWD1 a leaf-specific catalytic function. Supporting Evidence: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC207015/ Double mutant and twd1-1 show strongly reduced leaf expansion and strong epinastic growth behavior. |
| GO:0048439 flower morphogenesis | IMP PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | KEEP AS NON CORE | Summary: TWD1 regulates flower architecture and late stamen development. Reason: The full primary documents twd1 flower/petal and short-stamen phenotypes with complementation, and quantifies filament elongation, anther dehiscence and fertility. These are supported developmental outcomes of transporter regulation; missing short stamens and nectary defects should not be generalized to ABCB1/19 mutants, whose phenotypes differ. Supporting Evidence: url:https://oup.silverchair-cdn.com/article-minimal/6581225 Our analyses revealed that the FKBP42, TWISTED DWARF1 (TWD1), promotes stamen elongation and, to a lesser extent, anther dehiscence, as well as pollen maturation url:https://oup.silverchair-cdn.com/article-minimal/6581225 TWD1 mutation results in a reduced auxin flow in stamen filaments |
| GO:0048443 stamen development | IMP PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | KEEP AS NON CORE | Summary: TWD1 regulates flower architecture and late stamen development. Reason: The full primary documents twd1 flower/petal and short-stamen phenotypes with complementation, and quantifies filament elongation, anther dehiscence and fertility. These are supported developmental outcomes of transporter regulation; missing short stamens and nectary defects should not be generalized to ABCB1/19 mutants, whose phenotypes differ. Supporting Evidence: url:https://oup.silverchair-cdn.com/article-minimal/6581225 Our analyses revealed that the FKBP42, TWISTED DWARF1 (TWD1), promotes stamen elongation and, to a lesser extent, anther dehiscence, as well as pollen maturation url:https://oup.silverchair-cdn.com/article-minimal/6581225 TWD1 mutation results in a reduced auxin flow in stamen filaments |
| GO:0048461 flower structural organization | IMP PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | KEEP AS NON CORE | Summary: TWD1 regulates flower architecture and late stamen development. Reason: The full primary documents twd1 flower/petal and short-stamen phenotypes with complementation, and quantifies filament elongation, anther dehiscence and fertility. These are supported developmental outcomes of transporter regulation; missing short stamens and nectary defects should not be generalized to ABCB1/19 mutants, whose phenotypes differ. Supporting Evidence: url:https://oup.silverchair-cdn.com/article-minimal/6581225 Our analyses revealed that the FKBP42, TWISTED DWARF1 (TWD1), promotes stamen elongation and, to a lesser extent, anther dehiscence, as well as pollen maturation url:https://oup.silverchair-cdn.com/article-minimal/6581225 TWD1 mutation results in a reduced auxin flow in stamen filaments |
| GO:0051510 regulation of unidimensional cell growth | IMP PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | KEEP AS NON CORE | Summary: TWD1 regulates longitudinal growth of stamen epidermal cells. Reason: Figure1 directly measures shorter and wider stamen epidermal cells in twd1, with HA-TWD1 complementation. This supports regulation of one-dimensional growth and explains short filaments without requiring a change in epidermal cell identity. Supporting Evidence: url:https://oup.silverchair-cdn.com/article-minimal/6581225 the length of epidermal cells in the middle of twd |
| GO:0090627 plant epidermal cell differentiation | IMP PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | MARK AS OVER ANNOTATED | Summary: The stamen evidence measures epidermal cell dimensions rather than a differentiation transition. Reason: PMID35512423 Figure1 quantifies elongation and width in already epidermal cells. It does not establish acquisition of epidermal identity or a differentiation mechanism. The supported one-dimensional growth claim is retained separately; the differentiation interpretation exceeds this experiment without disproving other possible developmental roles. Supporting Evidence: url:https://oup.silverchair-cdn.com/article-minimal/6581225 the length of epidermal cells in the middle of twd |
| GO:1901703 protein localization involved in auxin polar transport | IMP PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | ACCEPT | Summary: TWD1 controls localization of ABCB proteins that execute polar auxin transport. Reason: Native root imaging and stamen ABCB1/19 localization establish the relevant transporter-trafficking role. The cargo specificity, client interactions and HSP90 cooperation go beyond a nonspecific necessity phenotype; the claim does not assign auxin transport itself to TWD1. Supporting Evidence: PMID:20971896 Mutations in TWD1 caused mislocalization of ABCB1, ABCB4, and ABCB19 to the ER instead of the plasma membrane url:https://oup.silverchair-cdn.com/article-minimal/6581225 both TWD1βCFP and ABCB1βGFP localized on the endothecium and middle layer plasma membrane PMID:41027915 serving as a co-chaperone of this ABC-FKBP-HSP90 dynamic module. |
| GO:2000012 regulation of auxin polar transport | IMP PMID:35512423 Arabidopsis TWISTED DWARF1 regulates stamen elongation by di... | ACCEPT | Summary: TWD1 regulates polar auxin transport by activating and maintaining selected ABCBs. Reason: Direct transport activation and native transporter localization support two separable contributions. TWD1 is not required for every PIN/ABCB transport route, and its substrate-specific vacuolar effects should not be conflated with auxin transport. Supporting Evidence: PMID:32699109 The D/E-P1008 motif is also important for ABCB1-TWD1 interactions and activation of ABCB1-mediated auxin transport by TWD1. PMID:20971896 Mutations in TWD1 caused mislocalization of ABCB1, ABCB4, and ABCB19 to the ER instead of the plasma membrane url:https://oup.silverchair-cdn.com/article-minimal/6581225 TWD1 mutation results in a reduced auxin flow in stamen filaments |
Loading supporting contentβ¦
Download this section (compressed HTML)Q: Does intact membrane-anchored TWD1 show the CaM-dependent PPIase activity measured for FKBD1β180, and can cis/trans conversion of an ABCB1 E1007βP1008 bond be measured directly?
Q: How do TWD1-mediated holdase/cochaperone functions and rapid transport activation contribute independently in different tissues?
Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)