The protein-RNA interaction in cowpea chlorotic mottle virus (CCMV) was evidently not altered during the pH-dependent swelling of the intact virus, as shown by 1H-NMR. Only a few CH2 and CH3 groups of amino acid side chains were mobile on a time scale of 10-7-10-8 s. Apparently, neither the RNA nor the N-terminal protein region were mobile on this time scale at any pH during the titrn. from pH 5.0 to 8.0 and back. The idea that the reported sensitivity of CCMV to proteases (at pH 7.5) might result from disclosure of previously hidden sites on subunit contact faces, rather than from a partial unfolding of the protein subunits themselves, was exptl. confirmed.
Vriend, G., Hemminga, M. A., Verduin, B. J. M., & Schaafsma, T. J. (1982). Swelling of cowpea chlorotic mottle virus studied by proton nuclear magnetic resonance. FEBS Letters, 146(2), 319–321. https://doi.org/10.1016/0014-5793(82)80943-5