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Publication Abstract from PubMed

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.

Disulfide bond stabilization of the hexameric capsomer of human immunodeficiency virus.,Pornillos O, Ganser-Pornillos BK, Banumathi S, Hua Y, Yeager M J Mol Biol. 2010 Sep 3;401(5):985-95. Epub 2010 Jun 26. PMID:20600115^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.