In the past decade major advances have been made towards understanding the mechanisms by which polytopic membrane proteins fold and assemble in cellular membranes. In eukaryotes, this process is mediated by a complex set of machinery in the endoplasmic reticulum (ER) that facilitates translocation of peptide loops across and integration of hydrophobic helices into the lipid bilayer. Studies evaluating the biogenesis of P-glycoprotein (P-gp) have been at the forefront of this rapidly expanding field. They have revealed a fascinating although sometimes confusing picture that has challenged our notions about general mechanisms of polytopic protein assembly and questioned specific predictions about the details and uniqueness of P-gp transmembrane topology. This review will attempt to summarize and consolidate our current knowledge of the sequence of events that gives rise to P-gp topology in the ER compartment and the implications of these events for polytopic protein biogenesis and function.
Keywords: P-glycoprotein, Cellular Membranes, TOPOLOGY, BIOGENESIS
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