[Formaldehyde-induced tight binding of protein to RNA in particles of rod-like viruses. Nature and specificity of the crosslinks].

A stable RNA-protein complex was obtained by treatment of a helical TMV-like virus - cucumber virus 4 (CV4) with 1.5% formaldehyde at 50 degrees C and stability and specificity of the RNA-protein bonds in the complex was studied. After alkaline of T2-RNAase hydrolysis of the complex obtained from the [32P]-labelled CV4, the RNA-protein crosslinks were identified by the presence of [32P] in the protein band during SDS electrophoresis in polyacrylamide gels. The resistance of the crosslinks to boiling in 2% SDS with 0.2% mercaptoethanol, to 0.3 N KOH and to 10% trichloracetic acid is indicative of the covalent nature of the nucleotide-protein bonds in the CV complex. Data from tryptic peptide map analysis suggest that not more than three peptides within the complex contain the [32P] label. It is concluded that formaldehyde crosslinks to the intravirus RNA only at the specific site(s) of the CV protein molecule.