title: Magic angle spinning NMR reveals sequence-dependent structural plasticity, dynamics, and the spacer peptide 1 conformation in HIV-1 capsid protein assemblies.
abstract: A key stage in HIV-1 maturation toward 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 intermediate using magic angle spinning (MAS) 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, 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.
authors.affiliation: Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States.
authors.forename: Yun
authors.initials: Y
authors.lastname: Han
authors.forename: Guangjin
authors.initials: G
authors.lastname: Hou
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Suiter
authors.forename: Jinwoo
authors.initials: J
authors.lastname: Ahn
authors.forename: In-Ja L
authors.initials: IJ
authors.lastname: Byeon
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Lipton
authors.forename: Sarah
authors.initials: S
authors.lastname: Burton
authors.forename: Ivan
authors.initials: I
authors.lastname: Hung
authors.forename: Peter L
authors.initials: PL
authors.lastname: Gor'kov
authors.forename: Zhehong
authors.initials: Z
authors.lastname: Gan
authors.forename: William
authors.initials: W
authors.lastname: Brey
authors.forename: David
authors.initials: D
authors.lastname: Rice
authors.forename: Angela M
authors.initials: AM
authors.lastname: Gronenborn
authors.forename: Tatyana
authors.initials: T
authors.lastname: Polenova
mesh_terms: D000595:Amino Acid Sequence; D036022:Capsid Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D015683:Gene Products, gag / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D015658:HIV Infections / Q000821:virology*; D015497:HIV-1 / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation
chemical_list: D036022:Capsid Proteins; D015683:Gene Products, gag