4PEX

Structure of the E502A variant of sacteLam55A from Streptomyces sp. SirexAA-E in complex with glucose

Summary for 4PEX

• Entry DOI: 10.2210/pdb4pex/pdb
• Related: 4PEW 4PEY 4PEZ 4PF0
• Descriptor: Putative secreted protein, 1,2-ETHANEDIOL, beta-D-glucopyranose, ... (4 entities in total)
• Functional Keywords: exo-beta-1, 3-glucanase, beta-1, gh55, glucose, secreted, biomass degradation, hydrolase
• Biological source: Streptomyces sp. SirexAA-E
• Total number of polymer chains: 2
• Total formula weight: 120635.77

Authors

Bianchetti, C.M.,Takasuka, T.E.,Yik, E.J.,Bergeman, L.F.,Fox, B.G. (deposition date: 2014-04-25, release date: 2015-03-18, Last modification date: 2023-09-27)

Primary citation

Bianchetti, C.M.,Takasuka, T.E.,Deutsch, S.,Udell, H.S.,Yik, E.J.,Bergeman, L.F.,Fox, B.G.
Active site and laminarin binding in glycoside hydrolase family 55.
J.Biol.Chem., 290:11819-11832, 2015

PubMed Abstract: The Carbohydrate Active Enzyme (CAZy) database indicates that glycoside hydrolase family 55 (GH55) contains both endo- and exo-β-1,3-glucanases. The founding structure in the GH55 is PcLam55A from the white rot fungus Phanerochaete chrysosporium (Ishida, T., Fushinobu, S., Kawai, R., Kitaoka, M., Igarashi, K., and Samejima, M. (2009) Crystal structure of glycoside hydrolase family 55 β-1,3-glucanase from the basidiomycete Phanerochaete chrysosporium. J. Biol. Chem. 284, 10100-10109). Here, we present high resolution crystal structures of bacterial SacteLam55A from the highly cellulolytic Streptomyces sp. SirexAA-E with bound substrates and product. These structures, along with mutagenesis and kinetic studies, implicate Glu-502 as the catalytic acid (as proposed earlier for Glu-663 in PcLam55A) and a proton relay network of four residues in activating water as the nucleophile. Further, a set of conserved aromatic residues that define the active site apparently enforce an exo-glucanase reactivity as demonstrated by exhaustive hydrolysis reactions with purified laminarioligosaccharides. Two additional aromatic residues that line the substrate-binding channel show substrate-dependent conformational flexibility that may promote processive reactivity of the bound oligosaccharide in the bacterial enzymes. Gene synthesis carried out on ∼30% of the GH55 family gave 34 active enzymes (19% functional coverage of the nonredundant members of GH55). These active enzymes reacted with only laminarin from a panel of 10 different soluble and insoluble polysaccharides and displayed a broad range of specific activities and optima for pH and temperature. Application of this experimental method provides a new, systematic way to annotate glycoside hydrolase phylogenetic space for functional properties.

PubMed: 25752603
DOI: 10.1074/jbc.M114.623579

Experimental method

X-RAY DIFFRACTION (1.75 Å)