Crystal structure and catalytic mechanism of PglD from Campylobacter jejuni.
The carbohydrate 2, 4-diacetamido-2, 4, 6-trideoxy-alpha-D-glucopyranose (BacAc(2)) is found in a variety of eubacterial pathogens. In Campylobacter jejuni, PglD acetylates the C4 amino group on UDP-2-acetamido-4-amino-2, 4, 6-trideoxy-alpha-D-glucopyranose (UDP-4-amino-sugar) to form UDP-BacAc(2). Sequence analysis predicts PglD to be a member of the left-handed beta helix family of enzymes. However, poor sequence homology between PglD and left-handed beta helix enzymes with existing structural data precludes unambiguous identification of the active site. The co-crystal structures of PglD in the presence of citrate, acetyl coenzyme A, or the UDP-4-amino-sugar were solved. The biological assembly is a trimer with one active site formed between two protomers. Residues lining the active site were identified, and results from functional assays on alanine mutants suggest His-125 is critical for catalysis, whereas His-15 and His-134 are involved in substrate binding. These results are discussed in the context of implications for proteins homologous to PglD in other pathogens.
Olivier
Nelson B
NB
Departments of Chemistry and Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.
Imperiali
Barbara
B
Departments of Chemistry and Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139. Electronic address: imper@mit.edu.
D000117:Acetylglucosamine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry; D000123:Acetyltransferases / Q000737:chemistry* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites / Q000502:physiology; D016123:Campylobacter jejuni / Q000201:enzymology*; D002384:Catalysis; D018360:Crystallography, X-Ray; D020836:Protein Structure, Quaternary / Q000502:physiology; D017433:Protein Structure, Secondary / Q000502:physiology; D040681:Structural Homology, Protein
C502751:2,4-diacetamido-2,4,6-trideoxyglucopyranose; D001426:Bacterial Proteins; D000123:Acetyltransferases; D000117:Acetylglucosamine