The disulfide loop of gp41 is critical to the furin recognition site of HIV gp160.
The importance of the HIV gp41 conserved disulfide loop to envelope function has been examined by mutational and functional analyses. Based on a luciferase-reporter entry assay, mutants gp41-CC/AA (C598A/C604A) and gp41-Delta (deletion of residues 596-606) result in a nonfunctional envelope protein. Western blot analysis shows both mutants to be properly expressed but not processed to form gp120 and gp41, which explains their nonfunctionality. The presence of mutant gp160 on the cell surface, as well as their ability to bind to sCD4, suggests that the mutations have disrupted processing at the furin recognition site encoded within the gp120 conserved domain 5, without resulting in an overall misfolding of the protein. With respect to the furin recognition site, the mutations are sequentially distant, which implies that the gp41 disulfide loop is interacting with gp120 C5 in gp160. In addition, we have modeled the gp120-gp41 interaction in unprocessed precursor gp160 using structural data available for gp120 and gp41 domains in isolation, supplemented by mutagenesis data. We suggest that the mutations have altered the interaction between gp120 C5 and the gp41 disulfide loop, resulting in decreased accessibility of the furin recognition site and implying that the interaction between the gp120 C5 and gp41 loop is a conformational requirement for gp160 processing. The sensitivity of this interaction could be exploited in future antivirals designed to disrupt HIV pathogenesis by disrupting gp160 processing.
Sen
Jayita
J
Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607, USA.
Jacobs
Amy
A
Jiang
Haiqing
H
Rong
Lijun
L
Caffrey
Michael
M
D001665:Binding Sites; D019921:Biotinylation; D015153:Blotting, Western; D002460:Cell Line; D003198:Computer Simulation; D019281:Dimerization; D005434:Flow Cytometry; D045683:Furin / Q000378:metabolism*; D006678:HIV / Q000235:genetics / Q000378:metabolism; D015699:HIV Envelope Protein gp120 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019302:HIV Envelope Protein gp160 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015700:HIV Envelope Protein gp41 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D017510:Protein Folding
D015699:HIV Envelope Protein gp120; D019302:HIV Envelope Protein gp160; D015700:HIV Envelope Protein gp41; D008156:Luciferases; D045683:Furin