Sea urchin axonemal motion supported by fluorescent, ribose-modified analogues of ATP

Abstract

The axonemal motion supported by fluorescent ribose-modified analogues, anthraniloyl ATP (Ant-ATP) and methylanthraniloyl ATP (Mant-ATP), was investigated. Ant-ATP and Mant-ATP supported good vigorous motion. A detailed study of the movement shows that the maximum beat frequencies (V_max) were significantly lower with the analogues. However, Michaelis constants (K_m) for beat frequency were also significantly lower than with ATP. Thus the net effect of changes in these two parameters, V_max/K_m, was similar for ATP and Ant-ATP and higher with Mant-ATP. Thus these fluorescent analogues are good substrates for axonemal movement. The consistently higher value of V_max/K_m, a measure of substrate selectivity, with Mant-ATP over Ant-ATP suggests a feature of the ribose binding site. Other significant differences in the movement with the fluorescent analogues are quantified in terms of kinetic measures of sliding velocity and bend propagation velocity.