Synthesis of Proteins in Tobacco Protoplasts Infected with Cowpea Chlorotic Mottle Virus

Summary The synthesis of proteins has been studied in tobacco protoplasts infected with cowpea chlorotic mottle virus (CCMV). Three new proteins were found with mol. wt. 19000 (P1), 34000 to 36000 (P2) and 100000 (P3). Protein P2 reached a maximum steady level about 16 to 20 h after infection; it was not a precursor of P1, which is virus coat protein. P3 appeared later than the other two proteins, reached its maximum about 44 h after infection and then declined. P2 and P3 were localized in the 1000 g and 20000 g pellets of a cell homogenate, in contrast to P1 (coat) which was largely found in the supernatant fraction after centrifuging at 20000 g for 30 min. The three proteins account for about 60% of the tripartite genome of CCMV.