Electrophoretic Properties of Cowpea Mosaic Virus (Severe Subgroup)

• Published in: Journal of general virology 1978-10, Vol.41 (1), p.155-160
• Main Authors: Thongmeearkom, Pornpod, Goodman, Robert M
• Format: Article
• Language: English
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/0022-1317-41-1-155

Department of Plant Pathology and International Soybean Program University of Illinois, Urbana, Ill. 61801, U.S.A. Particles of the Puerto Rico isolate of cowpea mosaic virus (CPMV-PR), which belongs in the severe subgroup, had one electrophoretic form when analysed by 2.5% polyacrylamide gel electrophoresis and zone electrophoresis in sucrose gradients at pH 7.8, 7.5, and 5.5. The electrophoretic properties of CPMV-PR did not vary with time after inoculation but the virus could be converted to a slower migrating form by in vitro treatment with trypsin. The partial conversion by trypsin was accompanied by and was possibly the result of proteolytic conversion of the S protein subunit to a lower molecular mass form. Analysis of proteins of untreated CPMV-PR suggested that the S subunit of the virus could also be converted in vivo by plant proteases to a smaller form without any change in the particle net surface charge, while in vitro treatment with trypsin affected those S subunits not previously converted by plant proteases, by converting them to a form slightly larger and with a greater positive charge than the S subunit produced by action of the plant proteases. This hypothesis accounts both for the decrease in electrophoretic mobility and for the fact that the conversion was only partial. * Present address: Section of Virology, Division of Plant Pathology, Department of Agriculture, Ministry of Agriculture and Cooperatives, Bangkok 9, Thailand. To whom reprint requests should be addressed. Received 28 March 1978; accepted 4 May 1978.