1tvp
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(New page: 200px<br /><applet load="1tvp" size="450" color="white" frame="true" align="right" spinBox="true" caption="1tvp, resolution 1.60Å" /> '''Endoglucanase cel5G ...)
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Revision as of 00:41, 25 November 2007
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Endoglucanase cel5G from Pseudoalteromonas haloplanktis in complex with cellobiose
Overview
Pseudoalteromonas haloplanktis is a psychrophilic Gram-negative bacterium, isolated in Antarctica, that lives on organic remains of algae. This, bacterium converts the cellulose, highly constitutive of algae, into an, immediate nutritive form by biodegrading this biopolymer. To understand, the mechanisms of cold adaptation of its enzymatic components, we studied, the structural properties of an endoglucanase, Cel5G, by complementary, methods, X-ray crystallography and small angle X-ray scattering. Using, X-ray crystallography, we determined the structure of the catalytic core, module of this family 5 endoglucanase, at 1.4A resolution in its native, form and at 1.6A in the cellobiose-bound form. The catalytic module of, Cel5G presents the (beta/alpha)(8)-barrel structure typical of clan GH-A, of glycoside hydrolase families. The structural comparison of the, catalytic core of Cel5G with the mesophilic catalytic core of Cel5A from, Erwinia chrysanthemi revealed modifications at the atomic level leading to, higher flexibility and thermolability, which might account for the higher, activity of Cel5G at low temperatures. Using small angle X-ray scattering, we further explored the structure at the entire enzyme level. We analyzed, the dimensions, shape, and conformation of Cel5G full length in solution, and especially of the linker between the catalytic module and the, cellulose-binding module. The results showed that the linker is, unstructured, and unusually long and flexible, a peculiarity that, distinguishes it from its mesophilic counterpart. Loops formed at the base, by disulfide bridges presumably add constraints to stabilize the most, extended conformations. These results suggest that the linker plays a, major role in cold adaptation of this psychrophilic enzyme, allowing, steric optimization of substrate accessibility.
About this Structure
1TVP is a Single protein structure of sequence from Pseudoalteromonas haloplanktis with CBI and EPE as ligands. Active as Cellulase, with EC number 3.2.1.4 Full crystallographic information is available from OCA.
Reference
Structure of a full length psychrophilic cellulase from Pseudoalteromonas haloplanktis revealed by X-ray diffraction and small angle X-ray scattering., Violot S, Aghajari N, Czjzek M, Feller G, Sonan GK, Gouet P, Gerday C, Haser R, Receveur-Brechot V, J Mol Biol. 2005 May 20;348(5):1211-24. Epub 2005 Mar 25. PMID:15854656
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