Taxonomic group: bacteria / Proteobacteria
(Phylum: Proteobacteria)
Associated disease: infection due to Escherichia coli [ICD11:
XN6P4 
]
NCBI PubMed ID: 16943443Journal NLM ID: 9211750Publisher: Woodbury, NY: Cold Spring Harbor Laboratory Press for the Protein Society
Correspondence: Hazel_Holden
biochem.wisc.edu
Institutions: Department of Biochemistry, University of Wisconsin, Madison, WI, USA
l-Colitose is a 3,6-dideoxysugar found in the O-antigens of some Gram-negative bacteria such as Escherichia coli and in marine bacteria such as Pseudoalteromonas tetraodonis. The focus of this investigation, GDP-4-keto-6-deoxy-d-mannose-3-dehydratase, catalyzes the third step in colitose production, which is the removal of the hydroxyl group at C3' of GDP-4-keto-6-deoxymannose. It is an especially intriguing PLP-dependent enzyme in that it acts as both a transaminase and a dehydratase. Here we present the first X-ray structure of this enzyme isolated from E. coli Strain 5a, type O55:H7. The two subunits of the protein form a tight dimer with a buried surface area of approximately 5000 A(2). This is a characteristic feature of the aspartate aminotransferase superfamily. Although the PLP-binding pocket is formed primarily by one subunit, there is a loop, delineated by Phe 240 to Glu 253 in the second subunit, that completes the active site architecture. The hydrated form of PLP was observed in one of the enzyme/cofactor complexes described here. Amino acid residues involved in anchoring the cofactor to the protein include Gly 56, Ser 57, Asp 159, Glu 162, and Ser 183 from one subunit and Asn 248 from the second monomer. In the second enzyme/cofactor complex reported, a glutamate ketimine intermediate was found trapped in the active site. Taken together, these two structures, along with previously reported biochemical data, support the role of His 188 as the active site base required for catalysis.
Molecular Structure, O-antigens, 3, colitose, PLP-dependent enzyme, 6-dideoxysugars
Structure type: monomer
Location inside paper: p.2094, scheme 1
Trivial name: componente of O-antigen, GDP-6-deoxy-D-lyxo-hexos-4-ulose
Compound class: nucleoside diphosphate sugar
Contained glycoepitopes: IEDB_141493,IEDB_149170,IEDB_190357
Methods: biochemical methods
Enzymes that release or process the structure: GDP-4-keto-6-deoxy-D-mannose-3-dehydratase
Related record ID(s): 20067, 20353, 20354, 20356
NCBI Taxonomy refs (TaxIDs): 562,
43659
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There is only one chemically distinct structure:
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