Refined measurement of SecA-driven protein secretion reveals that translocation is indirectly coupled to ATP turnover
Year: 2020
Type: article
Abstract: The universally conserved Sec system is the primary method cells utilize to transport proteins across membranes. Until recently, measuring the activity-a prerequisite for understanding how biological systems work-has been limited to discontinuous protein transport assays with poor time resolution or reported by large, nonnatural tags that perturb the process. The development of an assay based on a split superbright luciferase (NanoLuc) changed this. Here, we exploit this technology to unpick the steps that constitute posttranslational protein transport in bacteria. Under the conditions deployed, the transport of a model preprotein substrate (proSpy) occurs at 200 amino acids (aa) per minute, with SecA able to dissociate and rebind during transport. Prior to that, there is no evidence for a distinct, rate-limiting initiation event. Kinetic modeling suggests that SecA-driven transport activity is best described by a series of large (∼30 aa) steps, each coupled to hundreds of ATP hydrolysis events. The features we describe are consistent with a nondeterministic motor mechanism, such as a Brownian ratchet.
Institution: University of Bristol
Language: English
Subfield: Genetics
Domain: Life Sciences
Open Access status: green
Awards: Understanding mitochondrial protein import and membrane insertion., The Bacterial Secretosome, G3752187148, G3810972741, G3957247266, G4920555344, Deciphering the allosteric mechanism of protein translocation through membranes, Understanding mitochondrial protein import and membrane insertion.
OpenAlex ID: W3107929247