Molecular motors

Molecular motors couple a chemical energy potential to generate force over a distance that results in mechanical work. They share a common general ATPase mechanism in which the energy from ATP binding, hydrolysis and product release is utilized to drive conformational changes in the motor domain. These conformational changes can be amplified to a relatively large power stroke that is coupled to productive mechanical work. Within this common general ATPase utilization mechanism exists a wide diversity of enzymatic adaptations and unique structural organization. These diversifications of each molecular motor determine their specialization for specific biological functions. For example, the Myosin family of molecular motors shares high structural homology within the motor domain and conserved mechanochemical transduction pathways. However, the time transition between the biochemical intermediates and the dwelling times of the different structural states are diverse among the myosin family members and hence create a repertoire of myosins that are tailored for diverse functions in the cell. This often refers as the enzymatic adaptation of the motor domain for its cellular function. The sequence diversity in loops of highly mutation-prone regions in the polypeptide chain of the motor domain introduced by evolution is what drives motor diversification. Our research is aim to discover and to understand the enzymatic adaptations of molecular motors such as myosins, helicases and polymerases. We intend to leverage this knowledge in the future to engine

Studying Molecular Motors

The profound knowledge of the enzymatic adaptations requires a quantitative research that describes the biochemical reaction cycle of the molecular motor with “numbers”. To gain such quantitative knowledge of the individual rates and equilibrium constants of the reaction mechanism we study enzymology at millisecond time scale (Transient Kinetics). We also measure the equilibrium constants (Thermodynamics) of the different biochemical states along the ATPase cycle. Finally, we utilize kinetic simulation to evaluate the goodness of our model describing the motor behavior. The summation of the above studies enables us to derive a detailed enzymatic reaction mechanism, which converts into quantitative parameters such as the “duty ratio” of the motor (the fraction of time the motor dwell strongly bound to its track during its ATPase cycle), the thermodynamics coupling between the different ligated states, its cycling time and its rate limiting step. By this exact knowledge we can further understand the diversity found in the existing as well as in the new and unexplored molecular motors. Detailed quantitative analysis together of three dimensional structural determination and in vivo studies of molecular motors can potentially fully explain the behavior of these molecular motors in their natural environment-the cell.

Technology

Our lab utilizes advanced methodologies in recombinant DNA, protein engineering and novel protein expression/purification systems as well as state of the art instrumentation for biophysical characterization of enzymes. Students will be individually trained in all aspects of these disciplines. Many exciting new projects are now emerging in the lab that are in the heart of the central biological processes such as transcription, translation and organelle motility in eukaryotes. These quantitative studies will further increase our knowledge of enzyme’s behavior based on its reaction mechanism.

Selected Literature

Relating biochemistry and function in the myosin superfamily. Curr Opin Cell Biol. 2004, 16:61-7.De La Cruz EM, Ostep EM PubMed

Walking to work: roles for class V myosins as cargo transporters. Nat Rev Mol Cell Biol. 2011,13:13-26. Hammer JA 3rd, Sellers JR PubMed

Shaking the myosin family tree: biochemical kinetics defines four types of myosin motor. Semin Cell Dev Biol. 2011, 22:961-7. Bloemink MJ, Geeves MA PubMed