Resolving kinesin stepping: one head at a time

Kinesins are well-known to power diverse long-range transport processes in virtually all eukaryotic cells. The ATP-dependent processive stepping as well as the regulation of kinesin activity have thus been focus of extensive studies over the past decades. It is widely accepted that kinesin motors can self-regulate their activity by suppressing the catalytic activity of the heads. The distal random coil at the C-terminus, termed tail domain, is proposed to mediate this autoinhibition, however, a direct regulatory influence of the tail on the processive stepping of kinesin proved difficult to capture. Here, we simultaneously tracked the two distinct head domains in the kinesin-2 motor using dual-color super resolution microscopy (dcFIONA) and reveal for the first time their individual properties during processive stepping. We show that the autoinhibitory wild type conformation selectively impacts one head in the heterodimer but not the other. Our results provide key insights into the regulated kinesin stepping that had escaped experimental scrutiny.