The overall aims of this research are to understand the molecular mechanism by which actomyosin motility systems convert chemical energy into mechanical work, and to obtain a precise correlation between the mechanical, biochemical and structural events at the molecular level. Novel methods will be applied to non-muscle myosin molecular motors to probe the relations between biochemical reactions of the contractile proteins, the elementary mechanical steps of the cross-bridge cycle and the corresponding structural motions. Bifunctional, bi- arsenical and quantum rod fluorescent probes will be stably bound with known orientation to the motor domains, light chain subunits, and tails of the motors. The spatial orientation and translational position of these components will be monitored at high time resolution by novel single-molecule polarized fluorescence, total internal reflection (polTIRF) microscopy to determine the dynamics of specific protein structural changes during translocation along actin and under mechanical load. Increased time resolution recently achieved for measuring the rotational, translational, and thermal wobbling motions and will enable detailed events to be detected during the brief period of molecular stepping between stable dwell periods. An infrared optical trap, with high-speed feedback to clamp the actin in place and to rapidly measure the myosin working stroke after actin attachment, will be used to determine the specific relationships between release of ATPase products, phosphate and ADP, strengthening of the actomyosin bond, transition into force generating states, and tilting, resulting in movement of the cargo. The feedback optical trap will be combined with single-molecule polTIRF microscopy to directly evaluate the influence of mechanical stress, strain, and flexibility on stepping rates and protein orientation changes that relate to chemo-mechanical transduction. The energetics and statistics of actin subunit target selection will be determined from the orientation and force dependence of the domain angles, biochemical states and step sizes. The experiments will be carried out on non-muscle myosins isolated from recombinant expression systems. Results from this project should significantly advance knowledge of cell motility processes and thus bring a greater understanding of both normal and pathological states of neuronal and sensory-neural development and many other types of cell motility.
Myosin-based intracellular motility is crucial for development and maintenance of all of the organs in the body. The specific myosins to be studied here are required for appropriate neuronal development, sensori-neural function in hearing and eyesight, the immune response, and normal pigmentation. Thus errors of expression or function lead to severe developmental neurological deficits among many other diseases. The studies proposed here will give fundamental information on how intracellular transport myosins function and may eventually lead to explanations and therapeutic targets in these diseases.
|Lippert, Lisa G; Dadosh, Tali; Hadden, Jodi A et al. (2017) Angular measurements of the dynein ring reveal a stepping mechanism dependent on a flexible stalk. Proc Natl Acad Sci U S A 114:E4564-E4573|
|Lewis, John H; Jamiolkowski, Ryan M; Woody, Michael S et al. (2017) Deconvolution of Camera Instrument Response Functions. Biophys J 112:1214-1220|
|Woody, Michael S; Lewis, John H; Greenberg, Michael J et al. (2016) MEMLET: An Easy-to-Use Tool for Data Fitting and Model Comparison Using Maximum-Likelihood Estimation. Biophys J 111:273-282|
|Lippert, Lisa G; Hallock, Jeffrey T; Dadosh, Tali et al. (2016) NeutrAvidin Functionalization of CdSe/CdS Quantum Nanorods and Quantification of Biotin Binding Sites using Biotin-4-Fluorescein Fluorescence Quenching. Bioconjug Chem 27:562-8|
|Andrecka, J; Takagi, Y; Mickolajczyk, K J et al. (2016) Interferometric Scattering Microscopy for the Study of Molecular Motors. Methods Enzymol 581:517-539|
|Shroder, Deborah Y; Lippert, Lisa G; Goldman, Yale E (2016) Single molecule optical measurements of orientation and rotations of biological macromolecules. Methods Appl Fluoresc 4:042004|
|Beausang, John F; Shroder, Deborah Y; Nelson, Philip C et al. (2013) Tilting and wobble of myosin V by high-speed single-molecule polarized fluorescence microscopy. Biophys J 104:1263-73|
|Beausang, John F; Sun, Yujie; Quinlan, Margot E et al. (2012) Orientation and rotational motions of single molecules by polarized total internal reflection fluorescence microscopy (polTIRFM). Cold Spring Harb Protoc 2012:|
|Beausang, John F; Sun, Yujie; Quinlan, Margot E et al. (2012) Preparation of filamentous actin for polarized total internal reflection fluorescence microscopy (polTIRFM) motility assays. Cold Spring Harb Protoc 2012:|
|Beausang, John F; Sun, Yujie; Quinlan, Margot E et al. (2012) The polarized total internal reflection fluorescence microscopy (polTIRFM) twirling filament assay. Cold Spring Harb Protoc 2012:719-21|
Showing the most recent 10 out of 21 publications