Deviations from Arrhenius behavior of Kinesin-1 at low temperatures*

Kinesin-1 is a mechanochemical enzyme that is essential for executing long-distance transport of cargos in eukaryotic cells via processive motility along the microtubule network. KIF5A is a conventional kinesin in the Kinesin-1 family. The temperature dependence of enzymatic activity for several kinesin-1 motors has been reported to follow a simple Arrhenius trend. The range for this observation has been gradually extended to higher temperatures, as it became possible to circumvent and more recently control kinesin degradation. However, both biophysical and biochemical measurements to date have been limited down to ~5 °C. We investigated the enzymatic activity of KIF5A at even lower temperatures and have observed a break in the Arrhenius trend, corresponding to higher activation energy at lower temperature. We will report our investigations of this phenomenon in different biochemical backgrounds and discuss its cause as it relates to the nature of the rate-limiting step of kinesin’s enzymatic cycle.