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PDBsum entry 5e70
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References listed in PDB file
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Key reference
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Title
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Crystal structures of escherichia coli branching enzyme in complex with cyclodextrins.
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Authors
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L.Feng,
R.Fawaz,
S.Hovde,
F.Sheng,
M.Nosrati,
J.H.Geiger.
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Ref.
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Acta Crystallogr D Struct Biol, 2016,
72,
641-647.
[DOI no: ]
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PubMed id
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Abstract
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Branching enzyme (BE) is responsible for the third step in glycogen/starch
biosynthesis. It catalyzes the cleavage of α-1,4 glucan linkages and subsequent
reattachment to form α-1,6 branch points. These branches are crucial to the
final structure of glycogen and starch. The crystal structures of Escherichia
coli BE (EcBE) in complex with α-, β- and γ-cyclodextrin were determined in
order to better understand substrate binding. Four cyclodextrin-binding sites
were identified in EcBE; they were all located on the surface of the enzyme,
with none in the vicinity of the active site. While three of the sites were also
identified as linear polysaccharide-binding sites, one of the sites is specific
for cyclodextrins. In previous work three additional binding sites were
identified as exclusively binding linear malto-oligosaccharides. Comparison of
the binding sites shed light on this apparent specificity. Binding site IV is
located in the carbohydrate-binding module 48 (CBM48) domain of EcBE and
superimposes with the cyclodextrin-binding site found in the CBM48 domain of
5'-AMP-activated protein kinase (AMPK). Comparison of these sites shows the
similarities and differences in the two binding modes. While some of the binding
sites were found to be conserved between branching enzymes of different
organisms, some are quite divergent, indicating both similarities and
differences between oligosaccharide binding in branching enzymes from various
sources.
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