The p12 Domain Is Unstructured in a Murine Leukemia Virus p12-CAN Gag Construct

Sampson K Kyere,Michael F Summers,Prem Raj B Joseph,Vineet N Kewalramani

doi:10.1371/journal.pone.0001902

Sampson K Kyere, Michael F Summers + Show 2 more

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https://doi.org/10.1371/journal.pone.0001902

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Abstract

The Gag polyproteins of gammaretroviruses contain a conserved p12 domain between MA and CA that plays critical roles in virus assembly, reverse transcription and nuclear integration. Here we show using nuclear magnetic resonance, that p12 is unstructured in a Moloney murine leukemia virus (MMLV) Gag fragment that includes the N-terminal domain of CA (p12-CAN). Furthermore, no long range interactions were observed between the domains, as has been previously predicted. Flexibility appears to be a common feature of Gag “late” domains required for virus release during budding. Residues near the N-terminus of CAN that form a β-hairpin in the mature CA protein are unfolded in p12-CAN, consistent with proposals that hairpin formation helps trigger capsid assembly.

Highlights

All retroviruses encode a polyprotein called Gag that serves as the major structural protein of the virus and is capable of assembling into virus-like particles in the absence of any other viral constituent
Gag proteins contain three major domains: an Nterminal matrix (MA) domain that regulates intracellular trafficking and membrane targeting, a capsid (CA) domain that promotes virus assembly and forms the capsid shell of the viral core during proteolytic maturation, and a nucleocapsid (NC) domain that is responsible for genome selection and encapsidation
Gag proteins contain additional polypeptide elements and spacers that are often critical for proper virus assembly

Summary

Introduction

All retroviruses encode a polyprotein called Gag that serves as the major structural protein of the virus and is capable of assembling into virus-like particles in the absence of any other viral constituent. To gain insight into the dynamical properties of MMLV p12, {1H}–15N steady-state heteronuclear NOE (XNOE) data were obtained for the backbone 15N nuclei [31]. Initial examination of the 2D 1H,15N-HSQC spectra for p12CAN revealed a large subset of signals with poor chemical shift dispersion in the proton dimension, suggestive of a largely unstructured domain within the protein (Figure 1).

Results

Conclusion