Homology of egg and flagellar dynein. Comparison of ATP-binding sites and primary structure.

Unfertilized sea urchin eggs contain a Mg2+-ATPase which shares physical and enzymatic characteristics with dynein, the enzyme which powers ciliary and flagellar movement. To further investigate the homology of the egg ATPase and axonemal dynein, ATP-binding subunits in preparations of each of the enzymes were identified using a photoaffinity probe of ATP, 8-azido-ATP (8-N3ATP), and three high molecular weight (HMW) polypeptide components of the two enzymes were compared by one-dimensional peptide mapping. Two heavy chains (A and B) of both the flagellar and egg ATPases bound [alpha-32P]8-N3ATP. The labeling of the HMW bands was specifically inhibited by ATP or ADP. Both the cytoplasmic ATPase and flagellar dynein utilized 8-N3ATP as a substrate indicating that the reagent binds to the active site. The two HMW ATP-binding polypeptides and one other HMW component of the egg ATPase were compared to flagellar dynein heavy chains by peptide mapping. Digestion of the egg versus flagellar HMW polypeptides with Staphylococcus V8 protease or alpha-chymotrypsin produced a highly similar group of peptides, and each pair of heavy chains was qualitatively estimated to be over 85% homologous. These data support the identification of the egg ATPase heavy chains as components of a cytoplasmic dynein and suggest that the HMW polypeptides form active enzymatic sites in flagellar and egg dynein which are substantially homologous.