Determination of surface hydrophobicity of fast and slow myosins from rabbit skeletal muscles: Implication in heat-induced gelation

Both aliphatic and aromatic surface hydrophobicities of myosins from fast-twitch psoas major and slow-twitch semimembranosus proprius muscles were investigated using fluorescence probes (cis-parinaric acid and 8-analino-1-naphthalene sulphonic acid). Surface hydrophobicity of unheated slow myosin was 1 . 5-fold higher than that of fast myosin. However, heating led to an increased enhancement of fast myosin hydrophobicity which became, after heating, higher than that exhibited by heated slow myosin. Whatever the myosin isoforms, most surface hydrophobicity was on the myosin heads. Heating induced a rise in hydrophobicity of the S1-subfragment from slow and fast myosins. However, the hydrophobicity of rods from fast myosin was increased three-fold more by heating than did that from slow myosin. Finally, the blocking of hydrophobic binding sites affected differently the heat-induced gelation in high ionic strength (0 . 6 M KCl) of both myosin isoforms and confirmed that the molecular mechanisms involved in the gelation were muscle-type dependent.