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Publication Abstract from PubMed

Endo-beta-1,4-glucanase from thermophilic Fervidobacterium nodosum Rt17-B1 (FnCel5A), a new member of glycosyl hydrolase family 5, is highly thermostable and exhibits the highest activity on carboxymethylcellulose among the reported homologues. To understand the structural basis for the thermostability and catalytic mechanism, we report here the crystal structures of FnCel5A and the complex with glucose at atomic resolution. FnCel5A exhibited a (beta/alpha)8-barrel structure typical of clan GH-A of glycoside hydrolase families with a large and deep catalytic pocket located in the C-terminal end of the beta-strands, which may permit substrate access. A comparison of the structure of FnCel5A with related structures from thermopile Clostridium thermocellum, mesophile Clostridium cellulolyticum, and psychrophile Pseudoalteromonas haloplanktis showed significant differences in intra-molecular interactions (salt bridges and hydrogen bonds), which may account for the difference in their thermostabilities. The substrate complex structure in combination with a mutagenesis analysis of the catalytic residues implicates a distinctive catalytic module Glu167-His226-Glu283, which suggests that the histidine may function as an intermediate for the electron transfer network between the typical Glu-Glu catalytic module. Further investigation suggested that the aromatic residues Trp61, Trp204, Phe231, and Trp240 as well as polar residues Asn51, His127, Tyr228, and His235 in the active site not only participated in substrate binding, but also provided a unique micro-environment suitable for catalysis. These results provide substantial insight into the unique characteristics of FnCel5A for catalysis and adaptation to extreme temperature.

Crystal structure of hyperthermophilic Endo-beta-1,4-glucanase: Implications for catalytic mechanism and thermostability.,Zheng B, Yang W, Zhao X, Wang Y, Lou Z, Rao Z, Feng Y J Biol Chem. 2011 Nov 29. PMID:22128157^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.