Role of M protein aggregation in defective assembly of temperature-sensitive M protein mutants of vesicular stomatitis virus

Virology. 2000 Dec 20;278(2):520-33. doi: 10.1006/viro.2000.0675.


The goal of these experiments was to determine the steps in virus assembly that are defective at the nonpermissive temperature in temperature-sensitive (ts) matrix (M) protein mutants of vesicular stomatitis virus. It has been proposed that mutations in M protein either reduce the binding affinity for nucleocapsids or lead to aggregation, reducing the amount of M protein available for virus assembly. Cytosolic or membrane-derived M proteins from wild-type VSV and two ts M protein mutant viruses, tsM301 and tsO23, as well as a revertant of tsO23 virus, O23R1, were analyzed for binding to nucleocapsid-M protein (NCM) complexes and for M protein aggregation. The experiments presented here showed that ts M proteins synthesized at the nonpermissive temperature were capable of binding to nucleocapsids and that aggregation of ts M proteins did not reduce the amount of soluble M protein below the amount required for assembly of the O23R1 virus. Instead, the most pronounced defect in ts M proteins was in the ability of membrane-derived M proteins to be solubilized in the presence of the detergent Triton X-100. It is proposed that this detergent-insoluble form of M protein interferes with a step necessary to initiate assembly of NCM complexes. A similar detergent, Triton X-114, caused aggregation of membrane-derived wild-type M protein, disproving an earlier proposal that membrane-derived M protein behaves like an integral membrane protein in the presence of Triton X-114. Aggregation of wild-type M protein in the presence of Triton X-100 could be induced by incubation at 37 degrees C with a high-molecular-weight fraction isolated from uninfected cells by sucrose gradient centrifugation. These results implicate host components in inducing M protein aggregation.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Substitution
  • Animals
  • Cell Line
  • Cell Membrane / virology
  • Cricetinae
  • Cytosol / virology
  • Kinetics
  • Leucine
  • Nucleocapsid / chemistry
  • Nucleocapsid / physiology
  • Phenylalanine
  • Temperature
  • Vesicular stomatitis Indiana virus / genetics
  • Vesicular stomatitis Indiana virus / physiology*
  • Viral Matrix Proteins / chemistry
  • Viral Matrix Proteins / genetics
  • Viral Matrix Proteins / physiology*
  • Virion / genetics
  • Virion / physiology


  • Viral Matrix Proteins
  • Phenylalanine
  • Leucine