1ks8
From Proteopedia
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The structure of Endoglucanase from termite, Nasutitermes takasagoensis, at pH 2.5.
Overview
Contrary to conventional wisdom, it has been shown recently that termites, do not necessarily depend on symbiotic bacteria to process cellulose. They, secrete their own cellulases, mainly endo-beta-1,4-glucanase and, beta-1,4-glucosidase. Here, the first structure of an endogenous, endoglucanase from the higher termite Nasutitermes takasagoensis (NtEgl), is reported at 1.40 A resolution. NtEgl has the general folding of an, (alpha/alpha)(6) barrel, which is a common folding pattern for glycosyl, hydrolase family 9. Three-dimensional structural analysis shows that the, conserved Glu412 is the catalytic acid/base residue and the conserved, Asp54 or Asp57 is the base. The enzyme has a Ca(2+)-binding site near its, substrate-binding cleft. Comparison between the structure of the, Ca(2+)-free enzyme produced by reducing the pH of the soaked crystal from, 5.6 (the pH of optimum enzyme activity) to 2.5 with that of the, Ca(2+)-bound enzyme did not show significant differences in the locations, of the C(alpha) atoms. The main differences are in the conformation of the, residue side chains ligating the Ca(2+) ion. The overall structure of, NtEgl at pH 6.5 is similar to that at pH 5.6. The major change observed, was in the conformation of the side chain of the catalytic acid/base, Glu412, which rotates from a hydrophobic cavity to a relatively, hydrophilic environment. This side-chain displacement may decrease the, enzyme activity at higher pH.
About this Structure
1KS8 is a Single protein structure of sequence from Nasutitermes takasagoensis with SO4 as ligand. Active as Cellulase, with EC number 3.2.1.4 Full crystallographic information is available from OCA.
Reference
Structure of an endoglucanase from termite, Nasutitermes takasagoensis., Khademi S, Guarino LA, Watanabe H, Tokuda G, Meyer EF, Acta Crystallogr D Biol Crystallogr. 2002 Apr;58(Pt 4):653-9. Epub 2002, Mar 22. PMID:11914490
Page seeded by OCA on Sun Nov 25 01:51:24 2007
