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The heavy chain of rat brain cytoplasmic dynein, composed of four putative nucleotide-finding consensus sequences GX4GK(T/S) in the middle one third region, and inferred protein sequence are analogous to the sea urchin flagellar beta-dynein by 27.0% and to Dictyostelium cytoplasmic dynein by 53.5%. The N-terminal one third of the heavy chain of rat brain cytoplasmic dynein resembles the Dictyostelium cytoplasmic dynein by 43.8% and has a low resemblance of 19.4% to the sea urchin flagellar dynein. The inference shows that the N-terminal regions are different between sea urchin and Dictyostelium dyneins and that the C-terminal two-thirds of the dyneins function in the microtubule-dependent motility action.

The mechanism of MT depolymerization by KIF-Ms is explored by solving the crystal structure of the minimal functional domain of mouse KIF2C, a member of KIF-M, in two different nucleotide states. The mutational analysis to support the structural implications is presented and a structural model for the mechanism for MT depolymerization by KIF-M is proposed.