THE N-TERMINAL 31 AMINO-ACIDS OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 ENVELOPE PROTEIN GP120 CONTAIN A POTENTIAL GP41 CONTACT SITE

We have compared the expression of full-length gp 160 envelope protein from human immunodeficiency virus type 1 with that of a deletion mutant lacking the N-terminal 31 amino acids of the mature protein (gp160-DELTA-32). The gp160 and gp160-DELTA-32 proteins are processed to yield gp41 and gp120 or gp120-DELTA-32, respectively. In contrast to full-length gp120, gp120-DELTA-32 failed to associate with gp41 at the cell surface, despite conformational integrity as judged by soluble CD4 binding. Thus, the N-terminal 31 amino acids of gp120, which contain hyperconserved sequences, are likely involved in forming a contact site for gp41.