Role of M protein aggregation in defective assembly of temperature-sensitive M protein mutants of vesicular stomatitis virus.
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.
Flood
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Molecular Genetics Program, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1064, USA.
McKenzie
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MO
Lyles
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D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000821:virology; D006224:Cricetinae; D003600:Cytosol / Q000821:virology; D007700:Kinetics; D007930:Leucine; D019251:Nucleocapsid / Q000737:chemistry / Q000502:physiology; D010649:Phenylalanine; D013696:Temperature; D014721:Vesicular stomatitis Indiana virus / Q000235:genetics / Q000502:physiology*; D014763:Viral Matrix Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014771:Virion / Q000235:genetics / Q000502:physiology
D014763:Viral Matrix Proteins; D010649:Phenylalanine; D007930:Leucine