Crystallization and preliminary characterization of crystals of the C-terminal half fragment of tropomodulin.

Tropomodulin (40 kDa) stabilizes the actin-tropomyosin filament by capping the P end (slow-growing end). The C-terminal half (C20, 20 kDa), an independently folded domain that is believed to be responsible for the P-end capping, has been crystallized. Crystals grew in the presence of Zn(2+) as the solution pH was increased from 3 towards the pI of the protein. The crystals belong to the trigonal space group R3. They have unit-cell parameters a = b = 69.6, c = 101.3 A (mean values, with a estimated standard deviation of 0.009 A) and diffract to 1.9 A resolution when the frozen crystals were measured at 120 K on a rotating-anode X-ray source at 120 K.