Kar3Vik1, a member of the Kinesin-14 superfamily, shows a novel kinesin microtubule binding pattern

Abstract

The two head domains of the budding yeast Kinesin-14 Kar3Vik1 bind adjacent protofilaments at the start of the motility cycle, followed by release of Vik1 from one protofilament to allow the motor’s powerstroke.

Drosophila Ncd reveals an evolutionarily conserved powerstroke mechanism for homodimeric and heterodimeric kinesin-14s

“…Through our recent studies on S. cerevisiae Kar3Vik1 and Kar3Cik1, we discovered novel properties of these yeast kinesin14s that challenged the earlier models of how kinesin-14s generate force for their cellular functions (13,15,(26)(27)(28). The C-terminal globular domain of Vik1 exhibits the structure of a kinesin motor domain (MD), yet Vik1 as well as Cik1 lack a nucleotide-binding site (13,26).…”

“…In contrast to the microtubule (MT) plus-end directed processive kinesins, kinesin-14s are not processive as single molecules; they promote MT minus-enddirected force and use an ATP-promoted powerstroke to crosslink and slide one MT relative to another (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). Sequence analysis indicates that all members of the kinesin-14 subfamily are dimeric, yet the structural organization of kinesin-14 motors differs from the N-terminal processive kinesins.…”

“…The kinesin-14s exhibit C-terminal motor domains connected by an N-terminal continuous coiled-coil stalk with an N-terminal ATP-independent MT binding site (7,(18)(19)(20)(21)(22). And although most of the kinesin-14s are homodimeric, some yeast species, including Saccharomyces cerevisiae and Candida glabrata, contain heterodimeric kinesin-14s (13,14,19). The conventional hypothesis for homodimeric kinesin-14 force generation proposed that only one motor head interacts with the MT and only one ATP turnover is required to complete the powerstroke (Fig.…”

“…Because the C-terminal domain of Vik1 binds MTs independently of Kar3 and with high affinity (26), it was designated the Vik1 motor homology domain (MHD). A series of site-directed cross-links at the base of the coiled coil near the motor heads of Kar3Vik1 were introduced, and motility assays indicated that both the Kar3MD and Vik1MHD must interact with the MT lattice to generate sustained MT gliding, yet significant unwinding of the coiled coil was not required (>10 Å but <20 Å) (13). This series of experiments led to the proposal that Kar3Vik1 binds the MT lattice on adjacent MT protofilaments rather than a single protofilament in a head-to-tail fashion because such a small degree of unwinding of the coiled coil would not allow the 8-nm separation required for the two-head bound state.…”

“…The C-terminal globular domain of Vik1 exhibits the structure of a kinesin motor domain (MD), yet Vik1 as well as Cik1 lack a nucleotide-binding site (13,26). Because the C-terminal domain of Vik1 binds MTs independently of Kar3 and with high affinity (26), it was designated the Vik1 motor homology domain (MHD).…”