The effect of glutaraldehyde and phalloidin on the conformation of F-actin.

Recent data allow the assertion that conformational changes in F-actin regulate actin-myosin interaction in muscle fibre (Adelstein and Eisenberg 1980; Lednev 1980; Yanagida and Oosawa 1980; Borovikov et al. 1982; Borovikov and Gusev 1983 ; Borovikov and Karandashov 1983). However, the exact mechanism of such regulation cannot be established without further experimental evidence. The study of conformational changes in F-actin induced by glutaraldehyde or phalloidin (mushroom toxin phalloidin) seems to be of interest. These reagents cause no disturbances in actomyosin functions in a solution (Dancker et al. 1975 ; Mikawa et al. 1979), inhibiting, however, contraction in glycerinated muscle fibres (Bukatina and Morozov 1979; Prochniewicz-Nakayama and Yanagida 1982; Borovikov 1984). In the present study, we have shown that glutaraldehyde — and phalloidin — induced modifications of F-actin decrease the flexibility of thin filaments. Polarization UV fluorescent microscopy and birefringence methods were used.