Structure And Function Of HIV-1 Fusion Protein Gp41

Human immunodeficiency virus type 1 virus (HIV-1) fusion inhibitors is the third anti-HIV-1 drugs besides reverse transcriptase inhibitor and protease inhibitors. HIV-1 fusion inhibitors is different from reverse transcriptase inhibitor and protease inhibitors because it can inhibit for the entry of HIV-1 into target cells, thus to suppress the virus spread in the primary stage of the infection.In the year 2003, T20 (generic name:Enfuvirtide, brand name:Fusion) was approved by FDA and became the first HIV fusion inhibitor in the clinical application. Nowadays, there are many kinds of fusion inhibitors in development, which suggest the future development trend of anti AIDS drugsCellular entry of HIV-1 requires fusion of viral and cellular membranes Env is synthesized in the rough endoplasmic reticulum (ER) as the precursor polyprotein gp160, the gp160 precursor is transported into the Golgi network, where some of its oligosaccharide side chains are further processed, gp160 is cleaved by the proteases into the surface subunit gp120 and the transmembrane subunit gp41. The surface subunit gp120 is primarily involved in bingding of CD4 receptor and a coreceptor (CCR5 or CXCR4) on the target cells, which causes major conformational changes gp120 and expose gp41. Gp41 is responsible for fusion reaction.Crystallographic studies demonstrate that the core structure of HIV-1 gp41 is a stable six-helix bundle (6-HB) folded by its trimeric N-and C-terminal heptad repeats (NHR and CHR), and that a deep pocket (pocket-1) on the NHR helices (N-trimer) plays critical roles for 6-HB stability;however, previous crystal structures of HIV-1 gp41 core were determined by peptide fragments not containing the downstream sequence of pocket-1 thus the structural features of this site could not be observed. In this study, we identified a sub-pocket (designated pocket-2) on the N-trimer, which is located immediately downstream the pocket-1 and formed by a cluster of 7 residues including Leu587, Lys588 and Glu584 on one NHR helix and Tyr586, Val583, Ala582 and Arg579 of another NHR helix. Our mutagenesis studies showed that the pocket-2 residues play essential roles for HIV-1 Env-mediated cell entry and critically determine the antiviral activity of NHR-derived peptide fusion inhibitor T21. Biophysical experiments demonstrated that mutations of the pocket-2 residues could dramatically impair the thermostability and conformation of 6-HB structure and reduce the binding affinity of CHR-derived inhibitor HP23 that specifically targets the pocket-1 site. These data have provided useful information for the structure-function relationship of HIV-1 gp41 and for development of antiviral entry inhibitors.Through the study of crystal structure, we find that W623 may interact with pocket-2. We have made mutations with W623, the mutations study show that W623 is essential for HIV-1 entry and fusion, and is very important for HIV-1 Env-mediated cell entry and the antiviral activity of peptide fusion inhibitor T21. Biophysical experiments demonstrated that mutations of W623 could change thermostability and conformation of 6-HB structure. Then we designed peptides with W623 and find these peptides w have good antiviral effect. Indicates that the W623 has important value in the design of fusion inhibitors.In conclusion, studies herein evaluated the relationship between the structure and function of the gp41 protein pocket-2 and W623. The study suggests pocket-2 and W623 are importance in fusion inhibitor, and provides a new idea for the development of fusion inhibitor.