ANALYSIS OF A SALT STABLE MUTANT OF COWPEA CHLOROTIC MOTTLE VIRUS

An understanding of virion assembly and disassembly requires a detaile d understanding of the protein-protein and protein-nucleic acid intera ctions which stabilize the virion. We have characterized a mutant of c owpea chlorotic mottle virus (CCMV) that is altered in virion stabilit y. The mutant virions resist disassembly in 1.0 M NaCl, pH 7.5, wherea s the wild-type virions completely disassociate into RNA and capsid pr otein components. Sequence analysis of the mutant coat protein gene id entified a single A to G nucleotide change at position 1484 of RNA 3 ( position 134 of RNA 4), which results in a lysine to arginine change a t position 42 of the coat protein. Introduction of the K42R mutation i nto wild-type CCMV coat protein results in a salt stable virion phenot ype. Likewise, expression of the K42R mutant coat protein in Escherich ia coli followed by in vi?ro assembly produces virions that exhibit th e salt stable phenotype. Analysis of this mutation demonstrates how a single amino acid change in ?he primary structure of the coat protein leads to tertiary interactions which stabilize the virion. (C) 1996 Ac ademic Press, Inc.