Crystal structure of GH13 alpha-glucosidase GSJ from one of the deepest sea bacteria.

The crystal structure of the GH13 alpha-glucosidase (GSJ) from deep-sea bacterium Geobacillus sp. strain HTA-462 was determined to a 2.0 A resolution. Comparisons of the GSJ structure with that of other GH13 enzymes with different catalytic activities revealed that the catalytic cleft of GSJ was widely opened when compared with the homologues. The wide opening of the catalytic cleft originated from conformational changes of active site residues and disorder of the regions close to the catalytic center. This structural feature of GSJ would explain the ability of this enzyme to accept a wide variety of nonsugar molecules as acceptors in the transglycosylation reaction.