THE BLOUSE T-COMPLEX-ENCODED PROTEIN TCTEX-1 IS A LIGHT-CHAIN OF BRAIN CYTOPLASMIC DYNEIN

Mammalian brain cytoplasmic dynein contains three light chains of M(r) = 8,000, 14,000, add 22,000 (King, S. M., Barbarese, E., Dillman, J. F., III, Patel-King, R. S., Carson, J. H., and Pfister, K. Kr (1996) J . Biol. Chem. 271, 19358-19366). Peptide sequence data (16/16 residues correct) implicate the M(r) = 14,000 polypeptide as Tctex-1, a protei n encoded within the mouse t-complex. Tctex-1 cosediments with microtu bules and is eluted with ATP or salt but not with GTP as expected for a dynein subunit, The ATP-eluted protein precisely cosediments with kn own cytoplasmic dynein proteins in sucrose density gradients, Tctex-1 also is immunoprecipitated from brain and other tissue homogenates by a monoclonal antibody raised against the 74-kDa cytoplasmic dynein int ermediate chain, Quantitative densitometry indicates that Tctex-1 is a stoichiometric component of the dynein complex, As Tctex-1 is a candi date for involvement in the transmission ratio distortion (meiotic dri ve) of mouse t-haplotypes, these results suggest that cytoplasmic dyne in dysfunction may play an important role in non-mendelian chromosome segregation.