Low Sodium Dodecyl Sulfate Concentrations Inhibit Tobacco Mosaic Virus Coat Protein Amorphous Aggregation and Change the Protein Stability

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E. R. Rafikova, Yu. V. Panyukov, A. M. Arutyunyan, L. S. Yaguzhinsky, V. A. Drachev, and E. N. Dobrov^*

Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119992 Moscow, Russia; fax: (7-095) 939-3181; E-mail: dobrov@belozersky.msu.ru

^* To whom correspondence should be addressed.

Received May 6, 2004; Revision received June 1, 2004

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Effects of low SDS concentrations on amorphous aggregation of tobacco mosaic virus (TMV) coat protein (CP) at 52°C and on the protein structure were studied. It was found that SDS completely inhibits the TMV CP (11.5 µM) unordered aggregation at the detergent/CP molar ratio of 15 : 1 (0.005% SDS). As judged by fluorescence spectroscopy, these SDS concentrations did not prevent heating-induced disordering of the large-distance part of the TMV CP subunit, including the so-called “hydrophobic girdle”. At somewhat higher SDS/protein ratio (40 : 1) the detergent completely disrupted the TMV CP hydrophobic girdle structure even at room temperature. At the same time, these low SDS concentrations (15 : 1, 40 : 1) strongly stabilized the structure of the small-distance part of the TMV CP molecule (the four alpha-helix bundle) against thermal disordering as judged by the far-UV (200-250 nm) CD spectra. Possible mechanisms of TMV CP heating-induced unordered aggregation initiation are discussed.

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KEY WORDS: tobacco mosaic virus coat protein, amorphous aggregation, sodium dodecyl sulfate

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