M.W. Rees

Studies on alfalfa mosaic virus: I. The protein and nucleic acid

Abstract The molecular weight of the alfalfa mosaic virus (AMV) protein subunit was determined from amino acid analyses and specific staining for certain amino acids on peptide maps from tryptic and chymotryptic digests of the protein. A subunit molecular weight of 32,600 was confirmed by estimations of C-terminal and N-terminal residues and of the tryptophan content. AMV nucleic acid consisted of four components with sedimentation values of 24.3, 20.0, 17.3, and 12.7 S. The molecular weights of these components were estimated.

The amino acid composition, antigenicity, and other characteristics of the satellite viruses of tobacco necrosis virus

Abstract Three strains of the satellite (SV) of tobacco necrosis virus (TNV) were compared antigenically and in their ability to multiply with the help of different strains of TNV. Their antigenic specificity was not influenced by the strain of TNV but depended on the particular strain of SV used in the mixture. Antigenically the three strains were distinctly different, and this was reflected in the 49 changes in the amino acid composition of SV 1 and SV 2 . SV 1 and SV 2 multiplied well in mechanically inoculated leaves, whereas SV 3 did best in tobacco roots infected by the aid of the vector Olpidium brassicae . An ambient temperature of 36 °, which inhibited the multiplication of TNV, also affected SV. All strains crystallized readily and virus was lost in crystals during purification unless care was taken. From amino acid analysis and two-dimensional peptide maps, the molecular weight of the protein subunit of SV 1 was found to be 22,800 and to contain 208 amino acid residues. Of the 208 amino acid residues, 182 were accounted for in tryptic peptides separated by ion exchange and Sephadex chromatography. In the TNV and SV association, the RNA of SV codes for its coat protein. On the basis of the triplet code, the coding for the coat protein would require 624 of the 1200 nucleotides, and therefore SV can code for another protein. The help required by SV from TNV is discussed.

The amino acid sequence of the cowpea strain of tobacco mosaic virus protein

The amino acid sequence of the coat protein of the cowpea strain of tobacco mosaic virus (cowpea virus) has been determined. The tryptic peptide overlaps were obtained by digesting the protein with chymotrypsin and separating and analysing the lysine-and arginine-containing chymotryptic peptides. The primary structure of cowpea virus protein has been found to differ markedly from that of any other known strain of tobacco mosaic virus, and contains 3 amino acid residues more and 96 amino acid changes from the type strain. The significance of the distribution of those areas of the protein in which the amino acid residues are the same for all naturally occurring strains and chemically induced mutants of tobacco mosaic virus so far studied and the residues that form the important carboxyl-carboxylate pairs are discussed.

A mutant of cowpea chlorotic mottle virus with a perturbed assembly mechanism

Abstract A mutant of cowpea chlorotic mottle virus has been obtained in which the assembly mechanism operates about 1.5 pH units below that of wild-type virus. The structural behavior of the mutant is described as is the inheritance of its coat and density properties.

The tryptic peptides and terminal sequences of the protein from the cowpea strain of tobacco mosaic virus.

The use of ion exchange chromatography, gel filtration, and paper electrophoresis for the separation of the peptides obtained by tryptic digestion of the cowpea strain of tobacco mosaic virus protein is described. The amino acid compositions of the 13 tryptic peptides obtained were determined and accounted for 159 residues compared with the 158 found for type tobacco mosaic virus protein. The only tryptic peptide that cowpea tobacco mosaic virus protein and type tobacco mosaic virus protein have in common is asparaginyl-arginine despite the fact that the former is very similar to type tobacco mosaic virus protein in a number of its properties. The amino terminal sequence was found to be acetyl alanyl-tyrosine and the carboxyl terminal sequence was confirmed as alanine preceded by threonine.

Biochemical and serological comparisons between carnation yellow fleck virus and sugar beet yellows virus protein subunits.

Abstract Carnation yellow fleck virus is serologically related to sugar beet yellow virus. Amino acid analyses and tryptic peptide maps indicate about 50 amino acid differences between the proteins from the two viruses.

The primary structure of cowpea chlorotic mottle virus coat protein.

The amino acid sequence of the coat protein of wild-type cowpea chlorotic mottle virus has been nearly completely determined by direct methods. The sites of amino acid replacements were identified in the coat proteins of an oxidation-sensitive mutant, a temperature-sensitive mutant, and a salt-stable mutant. The replacements are a cysteinyl residue for the arginyl residue at position 25 in the oxidation-sensitive mutant, glutamic acid and alanine, respectively, for lysine and valine at positions 21 and 87 in the temperature-sensitive mutant, and arginine for lysine at position 105 in the salt-stable mutant. The substitutions are consistent with point mutations.