A Characterization of Alfalfa‐Mosaic‐Virus Protein Polymerization in the Presence of Nucleic Acid

Abstract

The polymerization of alfalfa mosaic virus (AMV) protein in the presence of homologous nucleic acids and a number of other natural and synthetic nucleic acids was studied. The conditions for optimal assembly were found to be pH 6.0 and low ionic strength ( I = 0.1 M) at room temperature, irrespective of the type of nucleic acid. The resulting nucleoprotein particles exhibited the same structural characteristics as the virus. This information emerged from optical diffraction and computer filtering of clcctron micrographs from the reconstituted particles.Irrespective of the type of nucleic acid present the polymerization of the protein resulting in a nucleoprotein particle is a cooperative process. Evidence for this was obtained by nitrocellulose filter binding assay, sodium dodecylsulphate/polyacrylamide gel electrophoresis, sedimentation velocity and electron microscopy of the reaction mixtures. The rates and efficiencies of reconstitution were of the same order of magnitude for a number of ribonucleic acids. Sedimentation data derived from AMV protein and AMV RNA mixtures suggested the existence of a specific nucleation product in the first stage of assembly. The results are discussed in terms of a tentative model of the assembly, in which at least two different steps (nucleation and elongation) can be distinguished, each characterized by an association constant.

The orientation of a T = 1 assembly of alfalfa mosaic virus coat protein in a hexagonal crystalline array

“…These protein dimers are able to aggregate, in the absence of RNA, into spherical T = 1 shells containing 30 dimers each (Driedonks, Krijgsman & Mellema, 1977). Similar spherical particles are obtained in the presence of nucleic acid (Hull, 1970;Lebeurier, Fraenkel-Conrat, Wurtz & Hirth, 1971;Driedonks, Krijgsman & Mellema, 1978).…”

The Primary Structure of the Coat Protein of Alfalfa Mosaic Virus Strain VRU. A Hypothesis on the Occurrence of Two Conformations in the Assembly of the Protein Shell

“…Similar unusually long particles were found in the case of strain 15/64 although at much lower frequencies [17]. The association behaviour of the VRU coat protein was studied by Driedonks et al using sedimentation analysis and electron microscopy [18]. The ability to form long particles was ascribed to the tendency of the protein to polymerize into tubular, rather than spherical, particles.…”

Specific RNA binding by amino-terminal peptides of alfalfa mosaic virus coat protein.

“…The flexible amino-terminus of CP extends to approximately amino acids 36-38 (van Beynum et al, 1977;Kan et al, 1982). The 3' untranslated region of A1MV RNA 4 contains a high affinity CP binding domain that was mapped by ribonuclease protection experiments (van Boxsel, 1976;Verhagen et al, 1976;Driedonks et al, 1978;Houwing and Jaspars, 1978). A homologous CP binding domain exists in the 3'-untranslated region of the three genomic AIMV RNAs (Koper-Zwartoff and Bol, 1980).…”