3MMU | pdb_00003mmu

Biochemical characterization and crystal structure of endoglucanase Cel5A from the hyperthermophilic Thermotoga maritima.

(2010) J Struct Biol 172: 372-379

• PubMed: 20599513 Search on PubMed
• DOI: https://doi.org/10.1016/j.jsb.2010.06.018
• Primary Citation of Related Structures:  
  3MMU, 3MMW


• PubMed 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 (β/α)(8) TIM-barrel fold in which the catalytic acid/base and nucleophile are located on strands β-4 and β-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 1.85Å 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.

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Organizational Affiliation: 

Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.