4AYS: The Structure Of Amylosucrase From D. Radiodurans

Amylosucrases (ASes) catalyze the formation of an alpha-1,4-glucosidic linkage by transferring a glucosyl unit from sucrose onto an acceptor alpha-1,4-glucan. To date, several ligand-bound crystal structures of wild-type and mutant ASes from Neisseria polysaccharea and Deinococcus geothermalis have been solved. These structures all display a very similar overall conformation with a deep pocket leading to the site for transglucosylation, subsite -1. This has led to speculation on how sucrose enters the active site during glucan elongation. In contrast to previous studies, the AS structure from D. radiodurans presented here has a completely empty -1 subsite. This structure is strikingly different from other AS structures, as an active-site-lining loop comprising residues Leu214-Asn225 is found in a previously unobserved conformation. In addition, a large loop harbouring the conserved active-site residues Asp133 and Tyr136 is disordered. The result of the changed loop conformations is that the active-site topology is radically changed, leaving subsite -1 exposed and partially dismantled. This structure provides novel insights into the dynamics of ASes and comprises the first structural support for an elongation mechanism that involves considerable conformational changes to modulate accessibility to the sucrose-binding site and thereby allows successive cycles of glucosyl-moiety transfer to a growing glucan chain.
PDB ID: 4AYSDownload
MMDB ID: 113324
PDB Deposition Date: 2012/6/21
Updated in MMDB: 2013/09
Experimental Method:
x-ray diffraction
Resolution: 3.15  Å
Source Organism:
Similar Structures:
Biological Unit for 4AYS: monomeric; determined by author and by software (PISA)
Molecular Components in 4AYS
Label Count Molecule
Protein (1 molecule)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB