Magic Angle Spinning NMR Reveals Sequence-Dependent Structural Plasticity, Dynamics, and the Spacer Peptide 1 Conformation in HIV-1 Capsid Protein Assemblies

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• 作者：Yun Han ; Guangjin Hou ; Christopher L. Suiter ; Jinwoo Ahn ; In-Ja L. Byeon ; Andrew S. Lipton ; Sarah Burton ; Ivan Hung ; Peter L. Gor鈥瞜ov ; Zhehong Gan ; William Brey ; David Rice ; Angela M. Gronenborn ; Tatyana Polenova
• 刊名：Journal of the American Chemical Society
• 出版年：2013
• 出版时间：November 27, 2013
• 年：2013
• 卷：135
• 期：47
• 页码：17793-17803
• 全文大小：771K
• 年卷期：v.135,no.47(November 27, 2013)
• ISSN：1520-5126

文摘

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.