Studies on the amino acid sequence of tobacco mosaic virus (TMV) protein. I. Fractionation of products of tryptic hydrolysis by countercurrent distribution

Abstract

Tobacco mosaic virus (TMV) protein (mol. wt. of subunit 18,270) was hydrolyzed with trypsin. The material soluble at pH 4.0 was fractionated by countercurrent distribution with the solvent system 2-butanol-0.1 M dichloroacetic acid. Preliminary investigations on these fractions have shown that nine apparently major tryptic hydrolysis products containing arginine and one containing lysine have been obtained from this fractionation. One arginine-containing peptide of large molecular weight was found in the portion of the digest insoluble at pH 4.0. One of these peptides has been found to contain arginine in both the N- and C-terminal positions. The nature and number of the N- and C-terminal residues produced as a result of the action of trypsin on TMV protein have been investigated. These results have revealed the presence of about one mole each of N-terminal glutamic acid, aspartic acid, serine, threonine, phenylalanine, tyrosine, and arginine and approximately two moles of glycine. Fractional amounts of N-terminal leucine and valine were also found. One mole each of C-terminal threonine and lysine and slightly more than nine moles of C-terminal arginine were determined.