Structural basis for the flexible recognition of α‐glucan substrates by Bacteroides thetaiotaomicron SusG. (17th April 2018)

• Record Type: Journal Article
• Authors: Arnal, Gregory; Cockburn, Darrell W.; Brumer, Harry; Koropatkin, Nicole M.
• Is Part Of: Protein science. Volume 27:Number 6(2018)
• Page Start: 1093
• Page End: 1101
• Publication Date: 2018-04-17
• Subjects: glycoside hydrolase family 13 (GH13) -- starch -- Bacteroides thetaiotaomicron -- SusG -- amylase; Proteins -- Periodicals; 572.6
• DOI: 10.1002/pro.3410
• Languages: English
• ISSNs: 0961-8368

Abstract

Abstract: Bacteria that reside in the mammalian intestinal tract efficiently hydrolyze dietary carbohydrates, including starch, that escape digestion in the small intestine. Starch is an abundant dietary carbohydrate comprised of α1, 4 and α1, 6 linked glucose, yet mammalian intestinal glucoamylases cannot effectively hydrolyze starch that has frequent α1, 6 branching as these structures hinder recognition and processing by α1, 4‐specific amylases. Here we present the structure of the cell surface amylase SusG from Bacteroides thetaiotaomicron complexed with a mixed linkage amylosaccharide generated from transglycosylation during crystallization. Although SusG is specific for α1, 4 glucosidic bonds, binding of this new oligosaccharide at the active site demonstrates that SusG can accommodate α1, 6 branch points at subsite −3 to −2, and also at subsite+1 adjacent to the site of hydrolysis, explaining how this enzyme may be able to process a wide range of limit dextrins in the intestinal environment. These data suggest that B. thetaiotaomicron and related organisms may have a selective advantage for amylosaccharide scavenging in the gut. Abstract : PDB Code(s):6BS6