Sugar recognition of lectin domain from ppGalNAc transferases involved in mucin-type O-glycosylation

ZLOCOWSKI N; IRAZOQUI FJ

Rosario, Argentina

Congreso; SAIB; 2006

SAIB

Mucin-type O-glycosylation is initiated by a large homologous family of polypeptide GalNAc-transferases (ppGalNAc-T). The glycosylation dependent activity for some ppGalNAc-T isoforms appears to be directed by a lectin domain (ld) found in the C-terminal of most ppGalNAc-Ts. In the present work we initiate the study of carbohydrate-binding specificity from ppGalNAc-T lds. The ld of ppGalNAc-T2 and T4 recognize GalNAc-MUC1, and this interaction showed inhibition in presence of GalNAc derivatives. The sugar recognition of ppGalNAc-T lds reveal changes if protein is cold, labelled with biotin, horseradish peroxidase or acetylated showing an effect of posttranslational modification in carbohydrate-binding specificity. The recognition of biotin ppGalNAc-T4 ld to GalNAc-MUC1 is reduced by presence of cold T11 ld, no affected by cold T4 ld and enhanced by cold T2 ld, showing a cooperation or competition in the interaction depending of each construct. In addition, western blot was used to study binding of soluble ppGalNAc-T2 against nucleus matrix of cell lines. Some bands of interaction are inhibited in presence of GlcNAc. Soluble ppGalNAc-T2 shows ability in the recognition of YSPT(GlcNAc)SPS glycopeptide that is commonly present in tandem repeats of C-terminal of RNA pol II polymerase. The sugar interaction of ppGalNAc-T lds could be involved in gene transcription and cell proliferation.