Journal:MicroPubl Biol:000669
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<StructureSection load='' size='450' side='right' scene='94/945522/Cv/1' caption=''> | <StructureSection load='' size='450' side='right' scene='94/945522/Cv/1' caption=''> | ||
===''Gossypium hirsutum'' gene Gohir.A03G007700.1 encodes a potential VAN3-binding protein with a phosphoinositide-binding site=== | ===''Gossypium hirsutum'' gene Gohir.A03G007700.1 encodes a potential VAN3-binding protein with a phosphoinositide-binding site=== | ||
- | <big> | + | <big>Emma R. Smith, Lauryn R. Caulley, Amanda M. Hulse-Kemp, Amanda R Storm, Angela K. Stoeckman</big> <ref>doi: 10.17912/micropub.biology.000669</ref> |
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<b>Molecular Tour</b><br> | <b>Molecular Tour</b><br> | ||
- | Based on our analyses, the uncharacterized Gossypium hirsutum protein (UniProt A0A1U8N485; NCBI XP_016732659) here referred to as GhVAB-A0A1U8N485, identified as a gene of unknown function in cotton species (Chen et al. 2020), contains two domains: a VAN3-binding protein-like, auxin canalisation domain (domain of unknown function, DUF828) and a pleckstrin homology (PH) domain. The specific function of these domains is unknown but they are often found together in proteins of the VAN3-binding (VAB) protein family, also known as the FORKED-like (FL) family. It is proposed that members of this plant-specific family in Arabidopsis are involved in aiding asymmetrical localization of PIN1 (PINFORMED) an auxin transport protein responsible for establishing vein patterns and numbers in leaves (Hou et al. 2010). GhVAB-A0A1U8N485 is most similar in sequence to the Group 3 FL proteins in Arabidopsis, FL5-7, which appear to be localized to the Golgi apparatus and decrease leaf size when mutated. | + | Based on our analyses, the uncharacterized ''Gossypium hirsutum'' protein (UniProt A0A1U8N485; NCBI XP_016732659) here referred to as GhVAB-A0A1U8N485, identified as a gene of unknown function in cotton species (Chen ''et al''., 2020<ref name='Chen'>PMID: 32313247</ref>), contains two domains: a VAN3-binding protein-like, auxin canalisation domain (domain of unknown function, DUF828) and a pleckstrin homology (PH) domain. The specific function of these domains is unknown but they are often found together in proteins of the VAN3-binding (VAB) protein family, also known as the FORKED-like (FL) family. It is proposed that members of this plant-specific family in Arabidopsis are involved in aiding asymmetrical localization of PIN1 (PINFORMED) an auxin transport protein responsible for establishing vein patterns and numbers in leaves (Hou ''et al''., 2010<ref name='Hou'>PMID: 20626652</ref>). GhVAB-A0A1U8N485 is most similar in sequence to the Group 3 FL proteins in Arabidopsis, FL5-7, which appear to be localized to the Golgi apparatus and decrease leaf size when mutated. |
- | The AlphaFold structure model for GhVAB-A0A1U8N485 predicted two distinct folding regions with high confidence from Gly111-Arg224 and Gln259-Val366. The first region, from residues 111-224, consists primarily of four alpha helices and contains most of the DUF828 domain. The second region contains the PH domain residues 259-366 and consists of a single alpha helix and seven anti-parallel beta sheets. Although VAB proteins are only found in plants, the PH domain structure is found in proteins across kingdoms of life. PH domains often localize to membranes, contain a conserved set of secondary structures and commonly bind phosphatidylinositol phosphates involved in signaling pathways (Le Huray et al. 2022). From published structures of other PH domains (Saccharomyces cerevisiae Avo1, PDB | + | The AlphaFold structure model for GhVAB-A0A1U8N485 predicted <scene name='94/945522/Cv/3'>two distinct folding regions with high confidence from Gly111-Arg224 and Gln259-Val366</scene>. The first region (colored in blue), from residues 111-224, consists primarily of four alpha helices and contains most of the DUF828 domain. The second region (in green) contains the PH domain residues 259-366 and consists of a single alpha helix and seven anti-parallel beta sheets. Although VAB proteins are only found in plants, the PH domain structure is found in proteins across kingdoms of life. PH domains often localize to membranes, contain a conserved set of secondary structures and commonly bind phosphatidylinositol phosphates involved in signaling pathways (Le Huray ''et al''., 2022<ref name='Huray'>PMID: 35857458</ref>). From published structures of other PH domains (''Saccharomyces cerevisiae'' Avo1, PDB [[3ulb]] and human protein kinase B/Akt, PDB [[1h10]]), the core of the PH domain is shown to be a seven-stranded anti-parallel beta-sandwich closed at its C-terminus by an alpha-helix. At the N-terminus of this beta-sandwich are three variable loops containing positively charged residues forming a pocket of basic residues that bind negatively-charged phosphoinositides. |
- | When the PH domain of human protein kinase B/Akt containing a bound phosphatidylinositol trisphosphate ligand (PDB | + | When the <scene name='94/945523/Cv/7'>PH domain of human protein kinase B/Akt (in pink) containing a bound phosphatidylinositol trisphosphate ligand (shown in ball-in-sticks; PDB [[1h10]]) was overlaid with the GhVAB-A0A1U8N485 PH domain (in orange)</scene>, a deep binding pocket accommodating the phosphoinositide ligand was observed in the structure. Indeed, <scene name='94/945523/Cv/9'>this GhVAB-A0A1U8N485 binding pocket is lined with positively-charged amino acids that could interact with the negatively-charge phosphate groups</scene> ({{Template:ColorKey_Charge_Anionic}} / {{Template:ColorKey_Charge_Cationic}}) and <scene name='94/945523/Cv/14'>residues within this pocket are highly-conserved based on ConSurf analysis</scene>. |
+ | [[Image:Consurf_key_small.gif|left]] | ||
+ | {{Clear}} | ||
- | < | + | A structure-based alignment between GhVAB-A0A1U8N485 and human protein kinase B/Akt indicated that two of the five ligand-binding residues in B/Akt are completely conserved in GhVAB-A0A1U8N485, with two others being conservative substitutions (Thomas ''et al''., 2002<ref name='Thomas'>PMID: 12176338</ref>). Evidence from sequence and structure features support that GhVAB-A0A1U8N485 is part of the VAN3-binding protein family. Furthermore, based on functional reports of other VAN3-binding proteins as well as structural analysis of our protein, GhVAB-A0A1U8N485 might be involved in regulating leaf size or vein development in cotton plants by binding phosphoinositides as part of an auxin signaling pathway. |
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<b>References</b><br> | <b>References</b><br> |
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