It is a pleasure to write an introduction for this collection of five short reviews of primate lentivirus Env proteins. These are
very timely reviews, each designed to cover a different aspect of the biology of these proteins. This is a remarkable time to
organize what we know about this family of proteins. There has been a long-standing interest in these proteins for their role in
viral entry. The Env protein is the only viral protein on the surface of the virion making it the sole protein involved in entry.
The synthesis of the Env protein is somewhat unremarkable, being a typical type 1 transmembrane protein synthesized as a
large precursor on the rough ER. There is the co-translational addition of carbohydrate within the ER and trimerization of the
Env protein precursor. Then in the golgi, a host protease cleaves the larger precursor into an extracellular surface protein (SU
subunit) and a transmembrane protein (TM subunit), creating a new N terminus of the TM protein that functions as the fusion
peptide in the fusion event. Despite this cleavage event, the SU and TM proteins remain together, with three of each subunit
comprising an Env trimer
