PDBsum entry 3mmu

Hydrolase

PDB id: 3mmu

Contents

Protein chains

(+ 2 more) 309 a.a.

Metals

_NI ×36

_CD ×20

Waters ×1199

References listed in PDB file

Key reference

• Title: Biochemical characterization and crystal structure of endoglucanase cel5a from the hyperthermophilic thermotoga maritima.
• Authors: J.H.Pereira, Z.Chen, R.P.Mcandrew, R.Sapra, S.R.Chhabra, K.L.Sale, B.A.Simmons, P.D.Adams.
• Ref.: J Struct Biol, 2010, 172, 372-379.
• PubMed id: 20599513

Abstract

Tm_Cel5A, which belongs to family 5 of the glycoside hydrolases, is an extremely stable enzyme among the endo-acting glycosidases present in the hyperthermophilic organism Thermotoga maritima. Members of GH5 family shows a common (beta/alpha)(8) TIM-barrel fold in which the catalytic acid/base and nucleophile are located on strands beta-4 and beta-7 of the barrel fold. Thermally resistant cellulases are desirable for lignocellulosic biofuels production and the Tm_Cel5A is an excellent candidate for use in the degradation of polysaccharides present on biomass. This paper describes two Tm_Cel5A structures (crystal forms I and II) solved at 2.20 and 1.85 A resolution, respectively. Our analyses of the Tm_Cel5A structure and comparison to a mesophilic GH5 provides a basis for the thermostability associated with Tm_Cel5A. Furthermore, both crystal forms of Tm_Cel5A possess a cadmium (Cd(2+)) ion bound between the two catalytic residues. Activity assays of Tm_Cel5A confirmed a strong inhibition effect in the presence of Cd(2+) metal ions demonstrating competition with the natural substrate for the active site. Based on the structural information we have obtained for Tm_Cel5A, protein bioengineering can be used to potentially increase the thermostability of mesophilic cellulase enzymes.