The amino-terminal peptide of HIV-1 glycoprotein 41 interacts with human erythrocyte membranes: peptide conformation, orientation and aggregation.
Structural studies assessed interactions between the amino-terminal peptide (FP-I; 23 residues 519-541) of the glycoprotein 41,000 (gp41) of Human Immunodeficiency Virus Type-1 (HIV-1) and human erythrocyte membranes and simulated membrane environments. Peptide binding was examined at sub-hemolytic (approx. less than 5 microM) and hemolytic (greater than or equal to 5 microM) doses (Mobley et al. (1992) Biochem. Biophys. Acta 1139, 251-256), using circular dichroism (CD) and Fourier-transform infrared (FTIR) measurements with FP-I, and electron spin resonance (ESR) studies employing FP-I spin-labeled at either the amino-terminal alanine (FP-II; residue 519) or methionine (FP-III; position 537). In the sub-lytic regime, FP-I binds to both erythrocyte lipids and dispersions of SDS with high alpha-helicity. Further, ESR spectra of FP-II labeled erythrocyte ghosts indicated peptide binding to both lipid and protein. In ghost lipids, FP-II was monomeric and exhibited low polarity and rapid, anisotropic motion about its long molecular axis (i.e., alpha-helical axis), with restricted motion away from this axis. The spin-label at the amino-terminal residue (Ala-519) is insensitive to the aqueous broadening agent chromium oxalate and buried within the hydrophobic core of the membrane; the angle that the alpha-helix (residues 519-536) makes to the normal of the bilayer plane is either 0 degree or 40 degrees. Contrarily, ESR spectra of ghost lipids labeled with sub-lytic doses of FP-III indicated high mobility and polarity for the reporter group (Met-537) at the aqueous-membrane interface, as well as extreme sensitivity to chromium oxalate. At lytic FP-I doses, CD and FTIR showed both alpha-helix and beta-structure for peptide in ghost lipids or detergent, while ESR spectra of high-loaded FP-II in ghost membranes indicated peptide aggregates. Membrane aggregates of FP-I may be involved in hemolysis, and models are suggested for N-terminal gp41 peptide participation in HIV-induced fusion and cytolysis.
Department of Pediatrics, King-Drew Medical Center/UCLA 90059.
L M
LM
Gordon
C C
CC
Curtain
Y C
YC
Zhong
A
A
Kirkpatrick
P W
PW
Mobley
A J
AJ
Waring
D000595:Amino Acid Sequence; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002942:Circular Dichroism; D003198:Computer Simulation; D004578:Electron Spin Resonance Spectroscopy; D004910:Erythrocyte Membrane / Q000378:metabolism*; D005583:Fourier Analysis; D015700:HIV Envelope Protein gp41 / Q000737:chemistry / Q000378:metabolism*; D006461:Hemolysis; D006801:Humans; D008555:Melitten / Q000494:pharmacology; D008563:Membrane Lipids / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared; D013113:Spin Labels
D015700:HIV Envelope Protein gp41; D008563:Membrane Lipids; D008565:Membrane Proteins; D010446:Peptide Fragments; D013113:Spin Labels; C076451:HIV envelope protein gp41 (519-541); D008555:Melitten