Abstract

Effects of low SDS concentrations on amorphous aggregation of tobacco mosaic virus (TMV) coat protein (CP) at 52 degrees C and on the protein structure were studied. It was found that SDS completely inhibits the TMV CP (11.5 microM) 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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