Microtubules (MT) are highly dynamic cylindrical-like structures within cells whose growth is controlled by motor proteins, a class of biological machines that walk along the MT while simultaneously regulating MT growth. Here we are interested in the behavior of kinesin-14 motor proteins. Although processive behavior of kinesin-14 motors has been studied, experts do not yet know how kinesin-14 motors are able to regulate MT growth; we aim to study the structure of two types of kinesin-14s to answer this question. Using Total Internal Reflection Fluorescence Microscopy we can observe kinesin-14 motor and MT interactions on a molecular level. My laboratory's previous results support the notion that a flexible structure is necessary for kinesin-14 regulation of microtubule dynamics. Here, we confirm that Ncd-3xGS(271) exhibits minus-end processivity and we show that Ncd-3xGS(271) protects the MT minus-end from depolymerization, in contrast to Ncd wild-type which does not exhibit processivity or regulation. Our results show that inducing a flexible polypeptide linker into the central stalk of Ncd allows this kinesin-14 motor to protect the MT minus-end from catastrophe events, which has further supported the notion that flexibility in the central stalk is an important mechanical determinant for both kinesin-14 motility and regulation.

Emily Eagen is a senior in Phsyics. Her research is supervised by Prof. Weihong Qiu.