Taxonomic group: bacteria / Proteobacteria
(Phylum: Proteobacteria)
Associated disease: infection due to Campylobacter jejuni [ICD11:
XN4Q5 
]
NCBI PubMed ID: 36534477Publication DOI: 10.1021/acs.biochem.2c00633Journal NLM ID: 0370623Publisher: American Chemical Society
Correspondence: H.M. Holden <hazel_holden
biochem.wisc.edu>; F.M. Raushel <raushel
tamu.edu>
Institutions: Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States, Department of Biochemistry & Biophysics, Texas A&M University, College Station, Texas 77843, United States, Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
Campylobacter jejuni is a human pathogen and the leading cause of food poisoning in the United States and Europe. Surrounding the exterior surface of this bacterium is a capsular polysaccharide (CPS) that consists of a repeating sequence of common and unusual carbohydrate segments. At least 10 different heptose sugars have thus far been identified in the various strains of C. jejuni. The accepted biosynthetic pathway for the construction of the 6-deoxy-heptoses begins with the 4,6-dehydration of GDP-d-glycero-d-manno-heptose by a dehydratase, followed by an epimerase that racemizes C3 and/or C5 of the product GDP-6-deoxy-4-keto-d-lyxo-heptose. In the final step, a C4-reductase catalyzes the NADPH reduction of the resulting 4-keto product. However, in some strains and serotypes of C. jejuni, there are two separate C4-reductases with different product specificities in the gene cluster for CPS formation. Five pairs of these tandem C4-reductases were isolated, and the catalytic properties were ascertained. In four out of five cases, one of the two C4-reductases is able to catalyze the isomerization of C3 and C5 of GDP-6-deoxy-4-keto-d-lyxo-heptose, in addition to the catalysis of the reduction of C4, thus bypassing the requirement for a separate C3/C5-isomerase. In each case, the 3'-end of the gene for the first C4-reductase contains a poly-G tract of 8-10 guanine residues that may be used to control the expression and/or catalytic activity of either C4-reductase. The three-dimensional structure of the C4-reductase from serotype HS:15, which only does a reduction of C4, was determined to 1.45 A resolution in the presence of NADPH and GDP.
serotype, capsular polysaccharide, Campylobacter jejuni, 6-deoxy-heptoses, C4-reductases
Structure type: polymer chemical repeating unit
Location inside paper: Fig. 1
Compound class: CPS
Contained glycoepitopes: IEDB_136907,IEDB_178410
Methods: 1H NMR, X-ray, SDS-PAGE, kinetics assays, ESI-MS, HPLC, crystallization, mutagenesis, enzyme structure, protein expression, plasmid constructs
Related record ID(s): 22338
NCBI Taxonomy refs (TaxIDs): 197Reference(s) to other database(s): GTC:G96134AE
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There is only one chemically distinct structure:
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