The dimerization domain of the HIV-1 capsid protein binds a capsid protein-derived peptide: a biophysical characterization.
The type 1 HIV presents a conical capsid formed by approximately 1500 units of the capsid protein, CA. Homodimerization of CA via its C-terminal domain, CA-C, constitutes a key step in virion assembly. CA-C dimerization is largely mediated by reciprocal interactions between residues of its second alpha-helix. Here, we show that an N-terminal-acetylated and C-terminal-amidated peptide, CAC1, comprising the sequence of the CA-C dimerization helix plus three flanking residues at each side, is able to form a complex with the entire CA-C domain. Thermal denaturation measurements followed by circular dichroism (CD), NMR, and size-exclusion chromatography provided evidence of the interaction between CAC1 and CA-C. The apparent dissociation constant of the heterocomplex formed by CA-C and CAC1 was determined by several biophysical techniques, namely, fluorescence (using an anthraniloyl-labeled peptide), affinity chromatography, and isothermal titration calorimetry. The three techniques yielded similar values for the apparent dissociation constant, in the order of 50 microM. This apparent dissociation constant was only five times higher than was the dissociation constant of both CA-C and the intact capsid protein homodimers (10 microM).
Garzón
María T
MT
Instituto de Biología Molecular y Celular, Edificio Torregaitán, Universidad Miguel Hernández, Avda. del Ferrocarril s/n, 03202 Elche (Alicante), Spain.
Lidón-Moya
María C
MC
Barrera
Francisco N
FN
Prieto
Alicia
A
Gómez
Javier
J
Mateu
Mauricio G
MG
Neira
José L
JL
D036022:Capsid Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D019281:Dimerization; D015497:HIV-1 / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence
D036022:Capsid Proteins