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Physiology and Biochemistry

The Effect of Limited Proteolysis on the Amino Acid Composition of Five Potyviruses and on the Serological Reaction and Peptide Map of the Tobacco Etch Virus Capsid Protein. Ernest Hiebert, Department of Plant Pathology, University of Florida, Gainesville 32611; J. H. Tremaine(2), and W. P. Ronald(3). (2)(3)Agriculture Canada, 6660 N.W. Marine Drive, Vancouver, B.C., Canada V6T 1X2. Phytopathology 74:411-416. Accepted for publication 19 October 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-411.

The capsid protein subunits of the selected potyviruses (tobacco etch [TEV], pepper mottle [PeMV], soybean mosaic, and watermelon mosaic 1 and 2) were studied after limited proteolysis in situ. The molecular weights of the protein subunits of these five viruses, estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, were in a range from 32,000 daltons (32 kd) to 35 kd before proteolysis and from 26 to 29 kd after proteolysis. Comparisons of amino acid analyses of nonproteolyzed and proteolyzed viral capsid protein for each virus showed that the cleaved portion of the subunit (~6 kd) had a high content of lysine. Electrophoresis of the capsid proteins of TEV cleaved by cyanogen bromide revealed the loss of two peptides after the limited proteolysis. Reaction of TEV with a lysyl-specific reagent 2,4,5-trinitrobenzenesulfonate before and after limited proteolysis, indicated that at least six lysyl residues per protein subunit were lost during the limited proteolysis of TEV. Serological tests indicated that some serological determinants are lost after limited proteolysis of TEV and PeMV. The amino acid compositions of the five potyviruses are compared with each other as well as with 10 other potyviruses from the literature, using Pearson' s correlation coefficients.

Additional keywords: capsid protein heterogeneity.