CHARACTERIZATION OF A DISASSEMBLY DEFICIENT MUTANT OF COWPEA CHLOROTIC MOTTLE VIRUS

An understanding of Virus disassembly requires a detailed understandin g of the protein-protein and protein-nucleic acid interactions which s tabilize the virion. We have characterized a mutant of cowpea chloroti c mottle virus [cpR26C (coat protein R26C)] that displays increased vi rion stability and is abnormal in virion disassembly when purified und er nonreducing conditions. Reduced virions are infectious, whereas non reduced virions are noninfectious. The cpR26C mutant virions purified under nonreducing conditions resist disassembly in 0.5 M CaCl2, pH 7.5 . The nonreduced cpR26C mutant virions swell in neutral pH conditions (pH 7.5) but do not disassociate when the ionic strength is increased. In contrast, wild-type Virions or cpR26C mutant virions isolated unde r reducing conditions completely disassociate into the RNA and capsid protein components at pH 7.5 and high ionic strength (i > 1.0). Sequen ce analysis of the cpR26C mutant identified a single C to U nucleotide change at position 1435 of RNA 3 (position 86 of RNA 4), which result s in a arginine to cysteine change at position 26 of the coat protein. The cpR26C mutant provides an ideal chemical switch for examining vir ion assembly and disassembly. (C) 1997 Academic Press