Taxonomic group: bacteria / Proteobacteria
(Phylum: Proteobacteria)
Associated disease: infection due to Escherichia coli [ICD11:
XN6P4 
]
NCBI PubMed ID: 18795799Journal NLM ID: 0370623Publisher: American Chemical Society
Correspondence: Hazel_Holden
biochem.wisc.edu
Institutions: Department of Biochemistry, UniVersity of Wisconsin, Madison, Wisconsin 53706
Perosamine (4-amino-4,6-dideoxy- d-mannose), or its N-acetylated form, is one of several dideoxy sugars found in the O-antigens of such infamous Gram-negative bacteria as Vibrio cholerae O1 and Escherichia coli O157:H7. It is added to the bacterial O-antigen via a nucleotide-linked version, namely GDP-perosamine. Three enzymes are required for the biosynthesis of GDP-perosamine starting from mannose 1-phosphate. The focus of this investigation is GDP-perosamine synthase from Caulobacter crescentus, which catalyzes the final step in GDP-perosamine synthesis, the conversion of GDP-4-keto-6-deoxymannose to GDP-perosamine. The enzyme is PLP-dependent and belongs to the aspartate aminotransferase superfamily. It contains the typically conserved active site lysine residue, which forms a Schiff base with the PLP cofactor. Two crystal structures were determined for this investigation: a site-directed mutant protein (K186A) complexed with GDP-perosamine and the wild-type enzyme complexed with an unnatural ligand, GDP-3-deoxyperosamine. These structures, determined to 1.6 and 1.7 A resolution, respectively, revealed the manner in which products, and presumably substrates, are accommodated within the active site pocket of GDP-perosamine synthase. Additional kinetic analyses using both the natural and unnatural substrates revealed that the K m for the unnatural substrate was unperturbed relative to that of the natural substrate, but the k cat was lowered by a factor of approximately 200. Taken together, these studies shed light on why GDP-perosamine synthase functions as an aminotransferase whereas another very similar PLP-dependent enzyme, GDP-4-keto-6-deoxy- d-mannose 3-dehydratase or ColD, catalyzes a dehydration reaction using the same substrate.
biosynthesis, O-antigen, Escherichia coli O157:H7, Vibrio cholerae O1, perosamine, synthase
Structure type: monomer
Location inside paper: p.10686, scheme 1
Trivial name: GDP-4-keto-3,6-dideoxymannose, GDP-4-keto-3,6-deoxymannose
Contained glycoepitopes: IEDB_141493,IEDB_149170,IEDB_190357
Methods: X-ray, sugar analysis, genetic methods, biochemical methods, HPLC, crystallization
Biological activity: biological activity data
Enzymes that release or process the structure: ColD (GDP-4-keto-6-deoxy-D-mannose-3-dehydratase)
Biosynthesis and genetic data: genetic data
3D data: molecular modeling
Related record ID(s): 22014, 22626, 22865, 22866, 22867, 22872, 22879
NCBI Taxonomy refs (TaxIDs): 83334,
127906
Show glycosyltransferases
There is only one chemically distinct structure:
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