Influence of acetylation on biological activity of polypeptide GalNAc-transferases.

ZLOCOWSKI NATACHA; LORENZ VIRGINIA; IRAZOQUI FERNANDO JOSÉ

Buenos Aires

Simposio; First Argentinian Symposium on Glycobiology "GlycoAR 2014"; 2014

Post-translational acetylation is an important molecularregulatory mechanism affecting the biological activity ofproteins. Polypeptide GalNAc transferases (ppGalNAc-Ts) area family of enzymes that catalyze initiation of mucin-type Oglycosylation.All ppGalNAc-Ts in mammals are type IItransmembrane proteins having a Golgi lumenal region thatcontains a catalytic domain with glycosyltransferase activity,and a C-terminal R-type ("ricin-like") lectin domain. Weinvestigated the effect of acetylation on catalytic activity ofglycosyltransferase, and on fine carbohydrate-bindingspecificity of the R-type lectin domain of ppGalNAc-T2. Massspectrometric analysis of acetylated ppGalNAc-T2 revealedseven acetylated amino acids (K103, S109, K111, K363, S373,K521, S529); the first five are located in the catalytic domain.Specific glycosyltransferase activity of ppGalNAc-T2 wasreduced 95% by acetylation. The last two amino acids, K521and S529, are located in the lectin domain, and theiracetylation results in alteration of the carbohydrate-bindingability of ppGalNAc-T2. Direct binding assays, competitiveassays and site-directed mutagenesis approaches showed thatacetylation of ppGalNAc-T2 modifies the fine GalNAc-bindingform of the lectin domain. Taken together, these findingsindicate that catalytic capacity and glycan-binding ability ofppGalNAc-T2 is regulated by acetylation.