Disulfide Bond Stabilization of the Hexameric Capsomer of Human Immunodeficiency Virus.Pornillos, O., Ganser-Pornillos, B.K., Banumathi, S., Hua, Y., Yeager, M.
(2010) J Mol Biol 401: 985-995
- PubMed: 20600115
- DOI: https://doi.org/10.1016/j.jmb.2010.06.042
- Primary Citation of Related Structures:
- PubMed Abstract:
The human immunodeficiency virus type 1 capsid is modeled as a fullerene cone that is composed of approximately 250 hexamers and 12 pentamers of the viral CA protein. Structures of CA hexamers have been difficult to obtain because the hexamer-stabilizing interactions are inherently weak, and CA tends to spontaneously assemble into capsid-like particles. Here, we describe a two-step biochemical strategy to obtain soluble CA hexamers for crystallization. First, the hexamer was stabilized by engineering disulfide cross-links (either A14C/E45C or A42C/T54C) between the N-terminal domains of adjacent subunits. Second, the cross-linked hexamers were prevented from polymerizing further into hyperstable capsid-like structures by mutations (W184A and M185A) that interfered with dimeric association between the C-terminal domains that link adjacent hexamers. The structures of two different cross-linked CA hexamers were nearly identical, and we combined the non-mutated portions of the structures to generate an atomic resolution model for the native hexamer. This hybrid approach for structure determination should be applicable to other viral capsomers and protein-protein complexes in general.
Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA.