Kinetic Studies of the Flagellar Movement of Sea-Urchin Spermatozoa

Abstract

The movements of intact and glycerinated spermatozoa from two species of sea-urchin were examined in the range of temperature between.5 and 30° C. The variations of the frequency of the glycerinated spermatozoa with changing pH, dielectric constant and ionic strength were examined. From the temperature studies values for activation entropies and enthalpies were obtained that pertain to the chemical reaction which limits the frequency. Within the limits of experimental error the activation parameters are identical for the intact spermatozoa and for the glycerinated model of the same species. The results are consistent with the hypothesis that the rate-limiting reaction is the breakdown of an enzyme-substrate complex. The pH studies suggest that neither the acidic nor the basic part of the enzyme is involved in complex formation but that both participate in the breakdown of the complex. The results obtained from the studies of dielectric constant are interpreted in terms of a model for the breakdown of the enzyme-substrate complex involving the separation of several spherical charges. The studies of pH and ionic strength suggest that both 14S and 30S dynein participate in the mechano-chemical process responsible for bending the flagellum.