Almost all the work in understanding how motor proteins work has been done under highly artificial conditions, abstracted from the cellular milieu in which the proteins actually work. Recent results demonstrate that the internal structure of the cell is pre-tensioned, and that generating, releasing, and sensing this tension is a key element in controlling how the cell reacts to its environment. We will observe single motors at work inside living cells. Our goal will be to understand how the cell generates, detects, and manages tension at the molecular level. The results from this project will be highly relevant to many aspects of human health, including heart disease, cancer metastasis, and the development of stem cell therapies. ('''Above''': An osmotic shock assay where a cell expands or contracts depending on the osmolarity of the solution it finds itself in. Cells use different mechanisms to protect themselves from situations of rapid increases or decreases in volume).
Understanding how myosin uses chemical energy to generate force and motion
Conventional myosin generates force in muscle, but other myosins play diverse biological roles, including transporting cargo throughout the cell. We will use sophisticated biophysical techniques to directly observe the motion of single myosin molecules in order to better understand how myosin converts chemical energy into useful motion. This project also has a more universal applicability. Recent work suggests that enzymes in general may derive their incredible catalytic ability by coupling protein motion to bond making and breaking. Single-molecule measurements on myosin offer a potentially powerful way to test this idea.
At right: A three bead optical tweezer setup to study the mechanism and function of motor proteins with nanometer spatial resolution and millisecond temporal resolution. The trace shows an example of an event (black) when the tweezer was oscillated (grey).
Design of new motor proteins
Artificial motor proteins have wide-ranging potential applications in fields like bottom-up nanofabrication, medical diagnostics, and responsive “smart” materials. Our group will use iterative rounds of protein design, screening, and single-molecule characterization to generate molecular motors with novel capabilities. Our work in creating novel motor proteins will test the validity and usefulness of the models of protein physics developed in Project 1.
At left: A de novo designed switch protein. The lever arm helix (red) packs across the scaffold helices (blue).
Measurement of force and motion inside living cells
Role of intercellular forces in cell and developmental biology:
The generation and detection of mechanical force is a central aspect of cell and developmental biology. Cells sense their physical surroundings by pulling on each other and the extracellular matrix (ECM). The resulting physical cues allow cells to communicate with each other, to coordinate complex collective movements, and to make critical decisions about cell growth and differentiation. Despite this central importance, the mechanisms by which cells exert and detect force remain poorly understood both in single cells and in whole organisms.
Our goal is to understand how cells generate, detect, and respond to tension at the molecular level. To do so, we are using new microscopy techniques that allow us to measure mechanical forces inside living cells, and even in whole organisms. The results from this project will be highly relevant to many aspects of human health, including heart disease, cancer metastasis, and the development of stem cell therapies, all of which are governed in part by the mechanical interactions of cells with their surroundings. (Above: An osmotic shock assay where a cell expands or contracts depending on the osmolarity of the solution it finds itself in. Cells use different mechanisms to protect themselves from situations of rapid increases or decreases in volume).