A study of the interaction of TMV protein with single- and double-stranded polynucleotides

Mechanism of RNA-protein interactions in tobacco mosaic virus: analysis of the pH stability of virus protein complexes with synthetic polynucleotides

TMV-like RNP complexes were reconstituted from TMV protein and synthetic polynucleotides. Analysis of the pH stability of RNP with polynucleotides containing U, G, or their analogues reveals a correlation between the stability of their structure and the pK values of the bases, and indicates that the -NH-CO-groups of U and G are involved in hydrogen bonding with protein. It is suggested that TMV protein has two U- and one G-specific binding sites which, according to the phase position of the protein subunits relative to the origin of TMV assembly (D. Zimmern (1977), Cell 11, 463) are likely to be organized as UGU. The binding of the A and C residues of RNA with TMV protein is nonspecific. TMV protein groups with pK 6.3, 7.5 and 9.7 were found to be essential in the protein-protein interactions in RNP. A group of the protein with pK 8.2 is also involved in RNP stabilization. Both protein-protein interactions and interactions of protein with RNA phosphate groups were shown to be mediated by a conformational change in the protein induced by base binding. The effect of bases on both types of interactions changes in the order G approximately equal to much greater than A, and incorporation of C in RNP proceeds in a compulsory way at the expense of interaction of the neighbouring nucleotide residues in polynucleotides with protein. The data obtained are used to discuss the principles of the cooperativity of the interactions between TMV components and the mechanism of initiation and elongation in TMV self-assembly.

Interaction of tobacco mosaic virus protein with synthetic polynucleotides containing a fluorescent label: optical properties of poly(A,epsilonA) and poly(C,epsilonC) copolymers and energy migration from the tryptophan to 1,N6-ethenoadenine or 3,N4-ethenocytosine residues in RNP

A spectrophotometric method for determination of the modification degrees and molar extinction coefficients for poly(A, epsilonA) and poly(C, epsilonC) copolymers has been developed. Dependence of some absorption and fluorescence parameters of the copolymers on the modification degree has been studied. Distribution of modified residues in copolymers differs from random and depends on modification conditions. Interaction between the TMV protein and copolymers has been investigated. The protein interacts with poly(A, epsilonA) of low or medium modification degree and displays no activity with respect to poly(epsilonA). On the contrary, introduction of epsilonC to the polynucleotide promotes complex formation between poly(C, epsilonC) and TMV protein. Analysis of the fluorescence emission and excitation spectra has revealed energy transfer from tryptophan to epsilonA or epsilon C in the RNP to occur and permits one to estimate the average distance between Trp (presumably Trp 52)o and the RNA base binding region in the virus to be 17 to 20 A.