The dimerization domain of the HIV‐1 capsid protein binds a capsid protein‐derived peptide: A biophysical characterization

Abstract

The type 1 HIV presents a conical capsid formed by ∼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 ␣-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 M. 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 M).

Ebselen, a Small-Molecule Capsid Inhibitor of HIV-1 Replication

“…A peptide mimicking the helix 9 sequence, CAC-1, was shown to inhibit CTD dimerization (21), and a stabilized version of this peptide, NYAD-201, inhibited mature-like virus particle formation (22). These results suggested that targeting CTD dimerization would be a good strategy to identify HIV inhibitors, and we initiated the development of an HTS-TR-FRET assay using the CTD of CA tagged with either GST (GST-CTD) or Flag (CTD-Flag) (Fig.…”

A Cell-penetrating Helical Peptide as a Potential HIV-1 Inhibitor

“…Backbone assignments of C-CA in the absence of peptide were made with a 380 μM U- 15 Owing to the poor solubility of NYAD-1, triple resonance experiments of the complex with C-CA were not feasible. However, the 1 H-15 N-heteronuclear single quantum coherence (HSQC) spectra of C-CA bound to NYAD-1 and NYAD-13 are nearly identical (Supplementary Data Fig.…”

“…Identification of peptides and small molecular compounds that disrupt HIV-1 assembly has been reported. [13][14][15][16][17][18] However, the mechanism of inhibition, especially for peptide inhibitors, has not been clearly demonstrated. The first breakthrough in identifying small-molecule inhibitors (CAP-1 and CAP-2) of CA was reported by Summers's group.…”

HIV Type 1 Gag as a Target for Antiviral Therapy

“…Neira and co-workers designed a synthetic peptide termed CAC1 that is based on the sequence of CA helix 9, and showed that it binds to the CTD in solution. 128 An in silico screening approach was used by Summers and colleagues to identify a small organic molecule,…”