title: Hydrophobic mutations in buried polar residues enhance HIV-1 gp41 N-terminal heptad repeat-C-terminal heptad repeat interactions and C-peptides' anti-HIV activity.
abstract: OBJECTIVE
  To investigate the effect of mutations in a highly conserved buried polar area on the function of HIV-1 gp41.
  
  
  METHODS
  During HIV-1 entry, a six helical bundle (6-HB) formation between the C-terminal and N-terminal heptad repeat (CHR and NHR) of gp41 provides energy for virus cell membrane fusion. In 6-HB, residues at a and d (a-d) positions of CHR directly interact with NHR and are buried. They are considered critical residues for 6-HB stability and for anti-HIV-1 activity of CHR-derived peptides (C-peptides). Most of a-d residues in CHR are hydrophobic, as buried hydrophobic residues facilitate protein stability. However, HIV-1 gp41 CHR contains a highly conserved polar area with four successive buried a-d polar residues: S649/Q652/N656/E659. We mutated these buried polar residues to hydrophobic residues, either Leu or Ile, and studied its effect on the gp41 NHR-CHR interactions and anti-HIV activities of the C-peptides.
  
  
  METHODS
  We measured the C-peptide mutants' ability to form 6-HB with NHR, thermal stability of the 6-HBs and C-peptides' inhibitory activity against both T20-sensitive and resistant HIV-1 strains.
  
  
  RESULTS
  All the mutated C-peptides retained their ability to form stable 6-HB with NHR and strongly inhibited HIV-1 replication. Strikingly, S649L and E659I mutations endow C-peptide with a significantly enhanced activity against T20-resistant HIV-1 strains.
  
  
  CONCLUSIONS
  The highly conserved buried a-d polar residues in HIV-1 gp41 CHR can be mutated as a means of developing new fusion inhibitors against drug-resistant HIV-1 strains. The concept can also be utilized to design fusion inhibitors against other viruses with similar mechanisms.
authors.affiliation: aMOE Key Laboratory of Structure-Based Drug Design & Discovery, Shenyang Pharmaceutical University, Shenyang bDepartment of Medicinal Chemistry, Beijing Institute of Pharmacology & Toxicology, Beijing cKey Laboratory of Medical Molecular Virology of MOE/MOH, Shanghai Medical College, Fudan University, Shanghai, China dLindsley F. Kimball Research Institute, New York Blood Center, New York, New York, USA. *Lifeng Cai, Keliang Liu and Shibo Jiang contributed equally to this work.
authors.forename: Baohua
authors.initials: B
authors.lastname: Zheng
authors.forename: Kun
authors.initials: K
authors.lastname: Wang
authors.forename: Lu
authors.initials: L
authors.lastname: Lu
authors.forename: Fei
authors.initials: F
authors.lastname: Yu
authors.forename: Maosheng
authors.initials: M
authors.lastname: Cheng
authors.forename: Shibo
authors.initials: S
authors.lastname: Jiang
authors.forename: Keliang
authors.initials: K
authors.lastname: Liu
authors.forename: Lifeng
authors.initials: L
authors.lastname: Cai
mesh_terms: D000595:Amino Acid Sequence; D019380:Anti-HIV Agents / Q000378:metabolism* / Q000494:pharmacology; D004252:DNA Mutational Analysis; D015700:HIV Envelope Protein gp41 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015497:HIV-1 / Q000187:drug effects / Q000502:physiology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D010455:Peptides / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D055550:Protein Stability; D053586:Virus Internalization
chemical_list: D019380:Anti-HIV Agents; D015700:HIV Envelope Protein gp41; D050505:Mutant Proteins; D010455:Peptides; C514787:gp41 protein, Human immunodeficiency virus 1