What is it about?

We have shown for the first time, the conformational changes happening in SecA ATPase undergoing catalysis. Our results show that precursor binding domain and C-terminal segment are highly dynamic during ATP hydrolysis and work in a nucleotide dependent manner

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Why is it important?

ATP is energy currency of cell. Understanding how an ATPase hydrolyses this molecule is of fundamental importance for many biological processes like protein secretion. Proteins to be exported are synthesized as precursors with an N-terminal leader sequence and are translocated through the Sec pathway in E. coli. SecA, the adenosine triphosphatase (ATPase) of the Sec system, binds to the translocon SecYEG to form a translocase. In a process that is currently not well understood, this complex mediates chemomechanical conversion that results in translocation of precursor proteins across the cytoplasmic membrane


We picked E. coli for this study as it is simple and easy to work with. We focused on imaging the consequences of a chemical reaction occurring within one particular protein that is responsible for transporting other newly synthesized proteins across the cell membrane. While we could not control the precise moment the reaction occurred due to its complexity, the force microscope's tapping motion allowed us to watch in real time how that protein changed its shape in response to exposure of a particular chemical and the release of chemical energy as the reaction happened in real time. These changes in shape of the protein are directly related to the its biological function. It is like making a movie of a single protein molecule doing its work in real time as it is happening. We are really in the early days of understanding the fine details of how cells work, even as simple as a bacteria, but as these tools become increasingly more precise and sophisticated, they could provide us with vital information in the future

Nagaraju Chada
Johns Hopkins University

Read the Original

This page is a summary of: Single-molecule observation of nucleotide induced conformational changes in basal SecA-ATP hydrolysis, Science Advances, October 2018, American Association for the Advancement of Science, DOI: 10.1126/sciadv.aat8797.
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