Magic Angle Spinning NMR Reveals Sequence-Dependent Structural Plasticity, Dynamics, and the Spacer Peptide 1 Conformation in HIV-1 Capsid Protein Assemblies.
Magic Angle Spinning NMR Reveals Sequence-Dependent Structural Plasticity, Dynamics, and the Spacer Peptide 1 Conformation in HIV-1 Capsid Protein Assemblies.
J Am Chem Soc. 2013 Oct 28;
Authors: Han Y, Hou G, Suiter CL, Ahn J, Byeon IJ, Lipton AS, Burton SD, Hung I, Gor'kov PL, Gan Z, Brey WW, Rice D, Gronenborn AM, Polenova TE
Abstract
A key stage in HIV-1 maturation towards an infectious virion requires sequential proteolytic cleavage of the Gag polyprotein leading to the formation of a conical capsid core that encloses the viral RNA genome and a small complement of proteins. The final step of this process involves severing the SP1 peptide from the CA-SP1 maturation intermediate, which triggers the condensation of the CA protein into the capsid shell. The details of the overall mechanism, including the conformation of the SP1 peptide in CA-SP1, are still under intense debate. In this report, we examine tubular assemblies of CA and the CA-SP1 maturation intermediates using Magic Angle Spinning NMR spectroscopy. At magnetic fields of 19.9 T and above, outstanding-quality 2D and 3D MAS NMR spectra were obtained for tubular CA and CA-SP1 assemblies yield, permitting resonance assignments for subsequent detailed structural characterization. Dipolar- and scalar-based correlation experiments unequivocally indicate that SP1 peptide is in a random coil conformation and mobile in the assembled CA-SP1. Analysis of two CA protein sequence variants reveals that, unexpectedly, the conformations of the SP1 tail, the functionally important CypA loop, and the loop preceding helix 8 are modulated by residue variations at distal sites. These findings provide support for the role of SP1 as a trigger of the disassembly of the immature CA capsid for its subsequent de novo reassembly into mature cores, and establish the importance of sequence-dependent conformational plasticity in CA assembly.
PMID: 24164646 [PubMed - as supplied by publisher]
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