Potato Virus X Coat Protein Research Articles

Translation of PVX RNA in vitro by wheat germ I. Characterization of the reaction and product size

Potato virus X (PVX) RNA was an efficient mRNA for in vitro translation by the wheat germ system. Optimal incorporation of labeled amino acids occurred in reaction mixtures (50 μl) containing 3 m M Mg 2+, 70 m M K +, and 3–4 μg of RNA. The presence of PVX RNA stimulated amino acid incorporation up to 40 times over background levels. Addition of spermine or spermidine further stimulated amino acid incorporation nearly twofold. PVX RNA translation was not inhibited by adding double-stranded RNA from Penicillium stoloniferum. The largest of several polypeptides obtained from PVX RNA translation reaction mixtures had an apparent molecular mass of 110,000 daltons. No polypeptide that coelectrophoresed with native PVX coat protein subunits was observed even when heat-treated PVX RNA was used, or when the products from spermine-stimulated reactions were analyzed.

The coat protein subunits of potato virus X and white clover mosaic virus, a comparison of methods for determining their molecular weights and some in situ degradation products of potato virus X protein

The molecular weight of potato virus X (PVX) coat protein subunit was determined to be 27,600 by SDS-polyacrylamide gel electrophoresis; 27,000 by gel chromatography in 0.1% SDS; 26,500 by gel chromatography in 6 M guanidine hydrochloride, and 26,800 by chemical analyses. Partial proteolysis, occurring after storage of some virus preparations at 4 o for more than 2 weeks, and presumably due to the action of a contaminating plant protease(s), is possibly responsible for the discrepancy between the earlier reported value of 22,300 and the presently determined values for the molecular weight of the PVX-protein of about 27,000. In addition to the in situ , partial degradation of PVX coat protein caused occasionally by a plant protease(s), it was found, in extension of an earlier report, that trypsin causes the cleavage in situ from PVX-protein of a specific peptide containing 24 amino acid residues. The molecular weight of white clover mosaic virus (WCMV) coat protein subunit was also determined by both SDS-polyacrylamide gel electrophoresis and gel chromatography in 6 M guanidine hydrochloride and the values obtained were identical—23,500.