Structural Basis for Coordination in Dimeric Kinesin

Kinesin-1 (conventional kinesin) is a protein motor that carries organelles and vesicle cargo along its microtubule track. The two catalytic heads of Kinesin-1 are linked to function as a highly processive "molecular walker'' that can take hundreds of steps before falling off the track. A key requirement for processivity is that the nucleotide cycles of the heads are coordinated to prevent simultaneous release of both heads from the track. The structural basis for coordination has not been established yet. Here, we show the conformational changes involved in nucleotide-dependent switching of the kinesin core in the functional context of the \MT. The observed conformational differences between two key nucleotide states comprise the structural groundwork for future studies on how the nucleotide cycles are coordinated between the heads. Further, a software suite, Ruby-Helix, was developed to facilitate helical image analysis and implement a new algorithm for the analysis of helical objects with a seam. Ruby-Helix incorporates several new techniques for conventional helical analysis, and automates many of the repetitive steps involved in helical analysis, thereby greatly increasing the throughput of this method.