The Haemophilus influenzae HMW1C protein is a glycosyltransferase that transfers hexose residues to asparagine sites in the HMW1 adhesin.
The Haemophilus influenzae HMW1 adhesin is a high-molecular weight protein that is secreted by the bacterial two-partner secretion pathway and mediates adherence to respiratory epithelium, an essential early step in the pathogenesis of H. influenzae disease. In recent work, we discovered that HMW1 is a glycoprotein and undergoes N-linked glycosylation at multiple asparagine residues with simple hexose units rather than N-acetylated hexose units, revealing an unusual N-glycosidic linkage and suggesting a new glycosyltransferase activity. Glycosylation protects HMW1 against premature degradation during the process of secretion and facilitates HMW1 tethering to the bacterial surface, a prerequisite for HMW1-mediated adherence. In the current study, we establish that the enzyme responsible for glycosylation of HMW1 is a protein called HMW1C, which is encoded by the hmw1 gene cluster and shares homology with a group of bacterial proteins that are generally associated with two-partner secretion systems. In addition, we demonstrate that HMW1C is capable of transferring glucose and galactose to HMW1 and is also able to generate hexose-hexose bonds. Our results define a new family of bacterial glycosyltransferases.
Department of Pediatrics, Duke University Medical Center, Durham, North Carolina, United States of America.
Susan
S
Grass
Cheryl F
CF
Lichti
R Reid
RR
Townsend
Julia
J
Gross
Joseph W
JW
St Geme
D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism*; D001216:Asparagine / Q000378:metabolism; D002853:Chromatography, Liquid; D005690:Galactose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006031:Glycosylation; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism*; D006193:Haemophilus influenzae / Q000201:enzymology* / Q000235:genetics; D006601:Hexoses / Q000378:metabolism*; D013058:Mass Spectrometry; D005810:Multigene Family / Q000502:physiology*; D016254:Mutagenesis, Insertional; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase / Q000235:genetics
D018829:Adhesins, Bacterial; C117431:HMW1 protein, bacteria; D006601:Hexoses; D001216:Asparagine; D016695:Glycosyltransferases; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase; D005947:Glucose; D005690:Galactose