Revision of estimates of the molecular weights of tobravirus coat proteins.

The molecular weights of proteins from several tobacco rattle viruses (or tobraviruses) have been determined by electrophoresis with 'marker' proteins in acrylamide gels of different strengths. Plotting KR, a measure of the effect of varying the gel strength, against molecular weight gave a value of 23,000 +/- 2,800 for tobacco rattle virus (TRV) strain CAM and similar values for other strains of TRV and pea early-browning virus. A value of 21,700 +/- 700 was obtained for TRV strain PRN by sedimentation to equilibrium in 6 M guanidine hydrochloride. These estimates are similar to those made by a statistical reappraisal of published data on amino acid composition, and a value of about 22,000 is proposed for TRV coat proteins.