DETERMINATION OF SURFACE HYDROPHOBICITY OF FAST AND SLOW MYOSINS FROMRABBIT SKELETAL-MUSCLES - IMPLICATION IN HEAT-INDUCED GELATION

Both aliphatic and aromatic surface hydrophobicities of myosins from f ast-twitch psoas major and slow-twitch semimembranosus proprius muscle s were investigated using fluorescence probes (cis-parinaric acid and 8-analino-1-naphthalene sulphonic acid). Surface hydrophobicity of unh eated slow myosin was 1 . 5-fold higher than that of fast myosin. Howe ver, heating led to an increased enhancement of fast myosin hydrophobi city which became, after heating, higher than that exhibited by heated slow myosin. Whatever the myosin isoforms, most surface hydrophobicit y was on the myosin heads. Heating induced a rise in hydrophobicity of the S1-subfragment from slow and fast myosins. However, the hydrophob icity of rods from fast myosin was increased three-fold more by heatin g 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 tha t the molecular mechanisms involved in the gelation were muscle-type d ependent.