Acetylation effect on biological activity of ppGalNAc-T2

ZLOCOWSKI N; JORGE A; NUÑEZ Y; IRAZOQUI FJ

Córdoba, Argentina

Congreso; Sociedad Argentina de Investigaciones Bioquímicas (SAIB); 2008

Sociedad Argentina de Investigaciones Bioquímicas (SAIB)

Polypeptide GalNAc-transferase, isoforme 2 (ppGalNAc-T2) is a member of the large family of polypeptide GalNAc-transferases involved in mucin-type O-glycosylation initiation. ppGalNAc-T are class II membrane protein with a small citoplasmatic domain (N-terminal), a transmembrane domain followed by the catalytic domain and a lectin domain (C-terminal). In the present work we study the influence of a post-translational modification, acetylation, on the biological activity of ppGalNAc-T2. The chemical acetylation of recombinant ppGalNAc-T2 reveals a critical reduction in catalytic activity on mucin-type O-glycosylation. MALDI-TOF mass spectrometry showed acetyl residues in Ser and Lys amine acids of catalytic and lectin domains of ppGalNAc-T2. Carbohydrate-binding ability of this protein is also influenced by acetylation, as observed by several approaches (dot blots, western blots, ELISAs, competitive assays), showing a major GalNAc recognition. The acetylation of Ser 529 and Lys 521 corresponding to high-conservative QKW domain of Ricin-type lectin family could be the motive of shift on the glycan-binding specificity of acetylated ppGalNAc-T2. The intracellular localization of acetylated ppGalNAc-T2, using specific antibody generated in our laboratory, in several conditions of different cell lines is in study.