4XSU

Crystal structure of Anabaena Alr3699/HepE in complex with UDP and glucose

Summary for 4XSU

• Entry DOI: 10.2210/pdb4xsu/pdb
• Related: 4xso 4xsp 4xsr
• Descriptor: Alr3699 protein, alpha-D-glucopyranose, URIDINE-5'-DIPHOSPHATE, ... (6 entities in total)
• Functional Keywords: gt-b fold, glycosyltransferase, transferase
• Biological source: Nostoc sp. (strain PCC 7120 / UTEX 2576)
• Total number of polymer chains: 2
• Total formula weight: 86872.20

Authors

Wang, X.P.,Dai, Y.N.,Jiang, Y.L.,Cheng, W.,Chen, Y.X.,Zhou, C.Z. (deposition date: 2015-01-22, release date: 2016-01-13, Last modification date: 2023-11-08)

Primary citation

Wang, X.P.,Jiang, Y.L.,Dai, Y.N.,Cheng, W.,Chen, Y.,Zhou, C.Z.
Structural and enzymatic analyses of a glucosyltransferase Alr3699/HepE involved in Anabaena heterocyst envelop polysaccharide biosynthesis
Glycobiology, 26:520-531, 2016

PubMed Abstract: Formation of the heterocyst envelope polysaccharide (HEP) is a key process for cyanobacterial heterocyst differentiation. The maturation of HEP in Anabaena sp. strain PCC 7120 is controlled by a gene cluster termed HEP island in addition to an operon alr3698-alr3699, which encodes two putative proteins termed Alr3698/HepD and Alr3699/HepE. Here we report the crystal structures of HepE in the apo-form and three complex forms that bind to UDP-glucose (UDPG), UDP&glucose, and UDP, respectively. The overall structure of HepE displays a typical GT-B fold of glycosyltransferases, comprising two separate β/α/β Rossmann-fold domains that form an inter-domain substrate-binding crevice. Structural analyses combined with enzymatic assays indicate that HepE is a glucosyltransferase using UDPG as a sugar donor. Further site-directed mutageneses enable us to assign the key residues that stabilize the sugar donor and putative acceptor. Based on the comparative structural analyses, we propose a putative catalytic cycle of HepE, which undergoes "open-closed-open" conformational changes upon binding to the substrates and release of products. These findings provide structural and catalytic insights into the first enzyme involved in the HEP biosynthesis pathway.

PubMed: 26692049
DOI: 10.1093/glycob/cwv167

Experimental method

X-RAY DIFFRACTION (2.48 Å)