Effects ofDeletions intheCytoplasmic Domainon Biological Functions ofHumanImmunodeficiency VirusType1 Envelope Glycoproteins

Theroleofthecytoplasmic domainofthehumanimmunodeficiency virus type1 (HIV-1) envelope glycoproteins invirus replication was investigated. Deletion ofresidues 840to856atthecarboxyl terminus of gp4lreduced theefficiency ofvirus entryduring an early stepinthevirus life cycle between CD4binding and formation oftheDNA provirus without affecting envelope glycoprotein synthesis, processing, or syncytiumforming ability. Deletion ofresidues aminoterminal toresidue 846was associated withdecreased stability of envelope glycoproteins madeinCOS-1cells, butthisphenotype was cell typedependent. Thecytoplasmic domainofgp4lwas notrequired fortheincorporation oftheHIV-1envelope glycoproteins into virions. These results suggest thatthecarboxyl terminus ofthegp4lcytoplasmic domainplays a role inHIV-1entryother thanreceptor binding ormembranefusion. Thecytoplasmic domainofgp4lalsoaffects thestability ofthe