The first structure of UDP-glucose dehydrogenase reveals the catalytic residues necessary for the two-fold oxidation.
Bacterial UDP-glucose dehydrogenase (UDPGlcDH) is essential for formation of the antiphagocytic capsule that protects many virulent bacteria such as Streptococcus pyogenes andStreptococcus pneumoniae type 3 from the host's immune system. We have determined the X-ray structures of both native and Cys260Ser UDPGlcDH from S. pyogenes (74% similarity to S. pneumoniae) in ternary complexes with UDP-xylose/NAD(+) and UDP-glucuronic acid/NAD(H), respectively. The 402 residue homodimeric UDPGlcDH is composed of an N-terminal NAD(+) dinucleotide binding domain and a C-terminal UDP-sugar binding domain connected by a long (48 A) central alpha-helix. The first 290 residues of UDPGlcDH share structural homology with 6-phosphogluconate dehydrogenase, including conservation of an active site lysine and asparagine that are implicated in the enzyme mechanism. Also proposed to participate in the catalytic mechanism are a threonine and a glutamate that hydrogen bond to a conserved active site water molecule suitably positioned for general acid/base catalysis.
Campbell
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RE
Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
Mosimann
S C
SC
van De Rijn
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I
Tanner
M E
ME
Strynadka
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NC
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D019281:Dimerization; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009243:NAD / Q000737:chemistry; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013297:Streptococcus pyogenes / Q000201:enzymology*; D014533:Uridine Diphosphate Glucose Dehydrogenase / Q000737:chemistry*; D014535:Uridine Diphosphate Glucuronic Acid / Q000737:chemistry; D014540:Uridine Diphosphate Xylose / Q000737:chemistry
D001426:Bacterial Proteins; D009243:NAD; D014535:Uridine Diphosphate Glucuronic Acid; D014540:Uridine Diphosphate Xylose; D014533:Uridine Diphosphate Glucose Dehydrogenase