The distinct protein and lipid constituents of the apical and basolateral membranes in
polarized cells are sorted by specific signals. O-Glycosylation of a highly polarized intestinal
brush-border protein sucrase isomaltase is implicated in its apical sorting through interaction
with sphingolipid-cholesterol microdomains. We characterized the structural determinants
required for this mechanism by focusing on two major domains in pro-SI, the membrane
anchor and the Ser/Thr-rich stalk domain. Deletion mutants lacking either domain, pro-SI …