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PDBsum entry 4xsu
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References listed in PDB file
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Key reference
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Title
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Structural and enzymatic analyses of a glucosyltransferase alr3699/hepe involved in anabaena heterocyst envelop polysaccharide biosynthesis.
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Authors
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X.P.Wang,
Y.L.Jiang,
Y.N.Dai,
W.Cheng,
Y.Chen,
C.Z.Zhou.
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Ref.
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Glycobiology, 2016,
26,
520-531.
[DOI no: ]
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PubMed id
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Abstract
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Formation of the heterocyst envelope polysaccharide (HEP) is a key process for
cyanobacterial heterocyst differentiation. The maturation of HEP inAnabaenasp.
strain PCC 7120 is controlled by a gene cluster termed HEP island in addition to
an operonalr3698-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.
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