It is generally assumed that preprotein substrates must be presented in an unfolded state to the bacterial Sec-translocase in order to be translocated. Here, we have examined the ability of the Sec-translocase to translocate folded preproteins. Tightly folded human cardiac Ig-like domain I27 fused to the C terminus of proOmpA is translocated efficiently by the Sec-translocase and the translocation kinetics are determined by the extent of folding of the titin I27 domain. Accumulation of specific translocation intermediates around the fusion point that undergo translocation progress upon ATP binding suggests that the motor protein SecA plays an important and decisive role in promoting unfolding of the titin I27 domain. It is concluded that the bacterial Sec-translocase is capable of actively unfolding preproteins.
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Protein translocation across cellular membranes is an essential and nano-scale dynamic process. In the bacterial cytoplasmic membrane, the core proteins in this process are a membrane protein complex, SecYEG, corresponding to the eukaryotic Sec61 complex, and a cytoplasmic protein, SecA ATPase. Despite more than three decades of extensive research on Sec proteins, from genetic experiments to cutting-edge single-molecule analyses, no study has visually demonstrated protein translocation.
View Article and Find Full Text PDFPhysical mechanisms of the Sec machinery operation.
Phys Chem Chem Phys
October 2024
Institute for Theoretical Physics, Johannes Kepler University Linz, Altenberger Strasse 69, A-4040 Linz, Austria.
The Sec complex, composed of a motor protein SecA and a channel SecYEG, is an ATP-driven molecular machine for the transport of proteins across the plasma membrane in bacteria. Today, there is a consensus about a general "rough" model of the complex activation and operation, which, however, lacks understanding of the physical mechanisms behind it. Molecular dynamics simulations were employed to address a way of allosteric activation, conformational transition of SecYEG from the closed to the open state, and driving forces of protein transport.
View Article and Find Full Text PDFThe Multifunctional Preprotein Binding Domain of SecA.
Chembiochem
December 2024
Department of Chemistry, University of Crete, Voutes, 70013, Heraklion, Greece.
Sec-pathway is the main protein secretion pathway in prokaryotes and is essential for their survival. The motor protein SecA is the main coordinator of the pathway in bacteria as it is has evolved to perform multiple tasks, acting like a "swiss army knife", from binding pre-proteins to altering its oligomeric and conformational states. This study focuses on the role of its Preprotein Binding Domain (PBD), which is a key protein module that identified in three conformational states (Wide-Open (WO), Open (O) and Closed (C)).
View Article and Find Full Text PDFWhole Cell Luminescence-Based Screen for Inhibitors of the Bacterial Sec Machinery.
Biochemistry
September 2024
School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom.
Article Synopsis
- There is an urgent need for new antibiotics due to increasing bacterial resistance to existing ones, with the bacterial Sec system being a promising target for this research.* -
- A new, scalable assay for screening Sec inhibitors using split NanoLuc luciferase has been developed, allowing for testing in living cells and distinguishing specific Sec targets.* -
- Initial tests on a library of 5000 compounds have identified some moderate inhibitors of Sec, showcasing the assay's effectiveness, with hopes for scaling up to find more potent options for drug development.*
A gene-rich mitochondrion with a unique ancestral protein transport system.
Curr Biol
August 2024
Unité d'Ecologie Systématique et Evolution, CNRS, Université Paris-Saclay, AgroParisTech, 91190 Gif-sur-Yvette, France. Electronic address:
Article Synopsis
- Mitochondria started from a special ancient relationship with a type of bacteria and lost many of their genes over time to just keep the important ones.
- Some modern mitochondria have very few genes, while others, like those in jakobids, have a lot, with some even having 91 genes like the new one found in Mantamonas sphyraenae.
- This special protist not only has many genes but also has a complete system for moving proteins into its mitochondria, showing it still keeps some ancient traits from its bacterial origins.
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