Relationship between human immunodeficiency virus type 1 Gag multimerization and membrane binding

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• The human immunodeficiency virus type 1 (HIV-1) Gag precursor, Pr55(Gag), drives viruslike particle assembly and release.
• Membrane binding and Gag-Gag multimerization are critical for HIV-1 assembly but their underlying domains and relationships are not fully understood.

Purpose of the Study:

• To investigate the domains responsible for HIV-1 Gag membrane binding and multimerization.
• To elucidate the relationship between membrane binding and Gag-Gag interactions during virus assembly.

Main Methods:

• Analysis of C-terminally truncated HIV-1 Gag mutants (MAstop, CA146stop, p41stop, p43stop, NC35stop) in vivo.
• Assessment of viruslike particle assembly, release, and copackaging with full-length Gag.
• Membrane flotation centrifugation to determine membrane-binding properties.

Main Results:

• Truncated Gag incorporation increased with extension from CA146 to NC35, indicating multiple Gag multimerization sites.
• The MA-only fragment showed reduced membrane binding compared to full-length Gag.
• The CA146 mutant (matrix and N-terminal capsid domains) exhibited membrane-binding levels similar to full-length Pr55(Gag).

Conclusions:

• Efficient HIV-1 Gag membrane binding can occur independently of strong Gag-Gag interaction domains.
• The matrix and N-terminal capsid domains of Gag are sufficient for effective steady-state membrane binding.
• These findings refine our understanding of the initial steps in HIV-1 particle formation.