IDENTIFICATION OF TUBULINS ASSOCIATED WITH THE 950 KDA PROTEASE FROM SALMON SPERM

We have previously identified the 650 kDa (20 S) proteasome and a high molecular mass (950 kDa) protease which contains the subunit with cro ss-reactivity with anti-20 S proteasome antibody in salmon sperm flage lla as candidates for ATP-dependent regulators of sperm motility (10). Here we further purified the 950 kDa protease without contamination o f 20 S proteasome by Mono Q ion-exchange column. Two-dimensional immun oblotting revealed that the 950 kDa protease still contained the 29 kD a proteasome subunit. The 950 kDa protease also contained 53 kDa doubl et as prominent components. Peptide mapping by V8 protease and chymotr ypsin, immunoblotting and immunoprecipitation revealed that the 53 kDa doublet were alpha- and beta-tubulin. The results suggest that this p rotease interacts with microtubules and is involved in the regulation of sperm motility.