Journal:MicroPubl Biol:000868

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We can also support whether the GhGH5BG-A0A1U8NW40 protein is a functional exo (1,3-β-glucosidase) by <scene name='10/1028493/Overlay3n9k/1'>comparing it to the structure of an experimentally studied enzyme such the exo-beta-1,3-glucanase</scene> from ''Candida albicans'' (PDB [[3n9k]]). GhGH5BG-A0A1U8NW40 GH5 domain is in cyan; actin-crosslinking domain: red; homologous exo-1,3- β-glucosidase XOG1 (PDB ID [[3n9k]]): bisque ribbon. The [[3n9k]] structure contains a substrate analog, <scene name='10/1028493/Overlay3n9k/2'>laminaritriose, that models into a deep pocket within the GH5 domain of both proteins when they are overlaid</scene>. Ball-and-stick representation of substrate analog laminaritriose (element coloring) and selected side chains (GH5-invariant residues: blue; catalytic residues: purple. Residues that are found in all active GH5 enzymes, including two catalytic glutamate residues, are all conserved in GhGH5BG-A0A1U8NW40 and the placement of these residues in the model align with the [[3n9k]] structure (Patrick ''et al''. 2010<ref name="Patrick">PMID: 20875088</ref>). Such information supports the prediction that GhGH5BG-A0A1U8NW40 is a catalytically active GH5 enzyme.
We can also support whether the GhGH5BG-A0A1U8NW40 protein is a functional exo (1,3-β-glucosidase) by <scene name='10/1028493/Overlay3n9k/1'>comparing it to the structure of an experimentally studied enzyme such the exo-beta-1,3-glucanase</scene> from ''Candida albicans'' (PDB [[3n9k]]). GhGH5BG-A0A1U8NW40 GH5 domain is in cyan; actin-crosslinking domain: red; homologous exo-1,3- β-glucosidase XOG1 (PDB ID [[3n9k]]): bisque ribbon. The [[3n9k]] structure contains a substrate analog, <scene name='10/1028493/Overlay3n9k/2'>laminaritriose, that models into a deep pocket within the GH5 domain of both proteins when they are overlaid</scene>. Ball-and-stick representation of substrate analog laminaritriose (element coloring) and selected side chains (GH5-invariant residues: blue; catalytic residues: purple. Residues that are found in all active GH5 enzymes, including two catalytic glutamate residues, are all conserved in GhGH5BG-A0A1U8NW40 and the placement of these residues in the model align with the [[3n9k]] structure (Patrick ''et al''. 2010<ref name="Patrick">PMID: 20875088</ref>). Such information supports the prediction that GhGH5BG-A0A1U8NW40 is a catalytically active GH5 enzyme.
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In addition to the GH5 domain, the GhGH5BG-A0A1U8NW40 protein has a second domain with structural homology to a certain fold found in Fascin proteins (IPR010431). Fascins are a family of actin-crosslinking proteins found across invertebrate and vertebrate eukaryotes, including humans, that are involved in the organization of the actin cytoskeleton and cell motility. The structure of Fascin proteins consists of four tandem β-trefoil fold subdomains. The GhGH5BG-A0A1U8NW40 protein has one of these β-trefoil fold subdomains which is interesting because no homologs of fascin proteins are found in plants. However, other studies have found that a plant-specific subfamily of GH5 proteins all have this fascin-like domain (Opassiri ''et al''. 2007<ref name="Opassiri">PMID: 17705786</ref>). The GhGH5BG-A0A1U8NW40 fascin-like domain does not contain the key residues required in Fascin proteins for crosslinking actin so this unique plant domain has likely evolved a different function, perhaps a new glucan-binding ability, but experimental studies are needed to explore this interesting feature.
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In addition to the GH5 domain, the GhGH5BG-A0A1U8NW40 protein has a second domain with structural homology to a certain fold found in Fascin proteins (IPR010431). Fascins are a family of actin-crosslinking proteins found across invertebrate and vertebrate eukaryotes, including humans, that are involved in the organization of the actin cytoskeleton and cell motility. The <scene name='10/1028493/Fascin/1'>structure of Fascin proteins consists of four tandem β-trefoil fold subdomains</scene> (human, PDB [[1dfc]]; each β-trefoil fold highlighted in a different color). The GhGH5BG-A0A1U8NW40 protein has one of these β-trefoil fold subdomains which is interesting because no homologs of fascin proteins are found in plants. However, other studies have found that a plant-specific subfamily of GH5 proteins all have this fascin-like domain (Opassiri ''et al''. 2007<ref name="Opassiri">PMID: 17705786</ref>). The GhGH5BG-A0A1U8NW40 fascin-like domain does not contain the key residues required in Fascin proteins for crosslinking actin so this unique plant domain has likely evolved a different function, perhaps a new glucan-binding ability, but experimental studies are needed to explore this interesting feature.
Fig 5 Structure of Fascin proteins (human, PDB 1DFC) with each β-trefoil fold highlighted in a different color.
Fig 5 Structure of Fascin proteins (human, PDB 1DFC) with each β-trefoil fold highlighted in a different color.

Revision as of 13:55, 12 February 2024

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