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Monomer-trimer equilibrium of the ectodomain of SIV gp41: Insight into the mechanism of peptide inhibition of HIV infection

Published online by Cambridge University Press:  01 September 1999

MICHAEL CAFFREY
Affiliation:
Laboratory of Chemical Physics, Building 5, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520
JOSHUA KAUFMAN
Affiliation:
Protein Expression Laboratory, Building 6B, National Institute of Arthritis and Musculoskeletal Diseases, National Institutes of Health, Bethesda, Maryland 20892
STEPHEN STAHL
Affiliation:
Protein Expression Laboratory, Building 6B, National Institute of Arthritis and Musculoskeletal Diseases, National Institutes of Health, Bethesda, Maryland 20892
PAUL WINGFIELD
Affiliation:
Protein Expression Laboratory, Building 6B, National Institute of Arthritis and Musculoskeletal Diseases, National Institutes of Health, Bethesda, Maryland 20892
ANGELA M. GRONENBORN
Affiliation:
Laboratory of Chemical Physics, Building 5, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520
G. MARIUS CLORE
Affiliation:
Laboratory of Chemical Physics, Building 5, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520
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Abstract

The monomer-trimer equilibrium of the ectodomain of SIV gp41 (residues 27–149, e-gp41) has been characterized by analytical ultracentrifugation, circular dichroism (CD), and NMR spectroscopy. Based on analytical ultracentrifugation experiments performed at different rotor speeds and protein concentrations, the equilibrium association constant for the SIV e-gp41 trimer is 3.1 × 1011 M−2. The presence of intermolecular nuclear Overhauser effects in a mixture of 12C and 13C-labeled e-gp41 prepared under nondenaturing conditions unambiguously demonstrates that there is a dynamic equilibrium between the monomer and trimer. The CD spectra taken as a function of SIV e-gp41 concentration suggest that the helical content of the monomeric state does not change significantly relative to that of the trimeric state. The relevance of the monomer-trimer equilibrium is discussed with respect to gp41 function and the inhibitory properties of gp41 peptides.

Type
FOR THE RECORD
Copyright
© 1999 The Protein Society

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