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

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 (Vmax) were significantly lower with the analogues. However, Michaelis constants (Km) for beat frequency were also significantly lower than with ATP. Thus the net effect of changes in these two parameters, Vmax/Km, 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 Vmax/Km, 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.