Structural Insights into the Glycosyltransferase Activity of the Actinobacillus pleuropneumoniae HMW1C-like Protein

• Published in: The Journal of biological chemistry Vol. 286; no. 44; pp. 38546 - 38557
• Main Authors: Kawai, Fumihiro, Grass, Susan, Kim, Youngchang, Choi, Kyoung-Jae, St. Geme, Joseph W., Yeo, Hye-Jeong
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 04.11.2011; American Society for Biochemistry and Molecular Biology
• Subjects: Actinobacillus pleuropneumoniae - metabolism; Adhesins, Bacterial - chemistry; Amino Acid Sequence; Bacteria; Binding Sites; Crystal Structure; Crystallography, X-Ray - methods; Enzyme Structure; Glycoprotein; Glycoproteins - chemistry; Glycosylation; Glycosyltransferase; Glycosyltransferases - chemistry; Haemophilus influenzae; Haemophilus influenzae - metabolism; Hexoses - chemistry; HMW1 Adhesin; HMW1C; Molecular Conformation; Molecular Sequence Data; Protein Structure and Folding; Protein Structure, Tertiary; Sequence Homology, Amino Acid; Two-Partner Secretion; Uridine Diphosphate - chemistry; Enzyme Structure; HMW1 Adhesin; Crystal Structure; Glycosyltransferase; Glycoprotein; Bacteria; Glycosylation; Two-Partner Secretion; HMW1C; Haemophilus influenzae
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111.237602

Glycosylation of proteins is a fundamental process that influences protein function. The Haemophilus influenzae HMW1 adhesin is an N-linked glycoprotein that mediates adherence to respiratory epithelium, an essential early step in the pathogenesis of H. influenzae disease. HMW1 is glycosylated by HMW1C, a novel glycosyltransferase in the GT41 family that creates N-glycosidic linkages with glucose and galactose at asparagine residues and di-glucose linkages at sites of glucose modification. Here we report the crystal structure of Actinobacillus pleuropneumoniae HMW1C (ApHMW1C), a functional homolog of HMW1C. The structure of ApHMW1C contains an N-terminal all α-domain (AAD) fold and a C-terminal GT-B fold with two Rossmann-like domains and lacks the tetratricopeptide repeat fold characteristic of the GT41 family. The GT-B fold harbors the binding site for UDP-hexose, and the interface of the AAD fold and the GT-B fold forms a unique groove with potential to accommodate the acceptor protein. Structure-based functional analyses demonstrated that the HMW1C protein shares the same structure as ApHMW1C and provided insights into the unique bi-functional activity of HMW1C and ApHMW1C, suggesting an explanation for the similarities and differences of the HMW1C-like proteins compared with other GT41 family members.