2c3v: Difference between revisions

Starch-hydrolyzing enzymes lacking alpha-glucan-specific, carbohydrate-binding modules (CBMs) typically have lowered activity on, granular starch relative to their counterparts with CBMs. Thus, consideration of starch recognition by CBMs is a key factor in, understanding granular starch hydrolysis. To this end, we have dissected, the modular structure of the maltohexaose-forming amylase from Bacillus, halodurans (C-125). This five-module protein comprises an N-terminal, family 13 catalytic module followed in order by two modules of unknown, function, a family 26 CBM (BhCBM26), and a family 25 CBM (BhCBM25). Here, we present a comprehensive structure-function analysis of starch and, alpha-glucooligosaccharide recognition by BhCBM25 and BhCBM26 using UV, methods, isothermal titration calorimetry, and x-ray crystallography. The, results reveal that the two CBMs bind alpha-glucooligosaccharides, particularly those containing alpha-1,6 linkages, with different, affinities but have similar abilities to bind granular starch. Notably, these CBMs appear to recognize the same binding sites in granular starch., The enhanced affinity of the tandem CBMs for granular starch is suggested, to be the main biological advantage for this enzyme to contain two CBMs., Structural studies of the native and ligand-bound forms of BhCBM25 and, BhCBM26 show a structurally conserved mode of ligand recognition but, through non-sequence-conserved residues. Comparison of these CBM, structures with other starch-specific CBM structures reveals a generally, conserved mode of starch recognition.

2C3V is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Bacillus_halodurans Bacillus halodurans] with IOD as [http://en.wikipedia.org/wiki/ligand ligand]. Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2C3V OCA].  

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