FIGURE 8.

Proposed molecular organization (schematic) of glycosyl-Ts in Golgi and extrinsic functions of lectin domains. A, flow of the sugar assembly line (S₀, initial substrate; P₁, product 1; P₂, product 2; P₃, product 3) is optimized by self-assembled glycosyl-T complex in Golgi. B, T3lec and T4lec have extrinsic inhibitory effects on ppGalNAc-T2 and -T3 activity (thin arrow). T3lec has an enhancing effect of Gal-transferase on dC1GalT enzyme (wide arrow). C, lectin domains of various ppGalNAc-T isoforms act as a regulatory scaffold to control glycosyl-T activities involved in O-GalNAc glycan biosynthesis.