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bioRxiv · 10.1101/2021.01.18.427065

A nexus of intrinsic dynamics underlies translocase priming

Krisnamurthy, S.·Eleftheriadis, N.·Karathanou, K.·Smit, J. H.·Portaliou, A.·Chatzi, K. E.·Karamanou, S.·Bondar, A.-N.·Gouridis, G.·Economou, A.
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Abstract

The cytoplasmic ATPase SecA and the membrane-embedded SecYEG channel assemble to form the functional Sec translocase. How this interaction primes and catalytically activates the translocase remains unclear. We now show that priming exploits a sophisticated nexus of intrinsic dynamics in SecA. Using atomistic simulations, single molecule FRET and hydrogen/deuterium exchange mass spectrometry we reveal multiple distributed dynamic islands that cross-talk with domain and quaternary motions. These dynamic elements are highly conserved and essential for function. Central to the nexus is a slender Stem through which, motions in the helicase ATPase domain of SecA biases how the preprotein binding domain rotates between open-closed clamping states. Multi-tier dynamics are enabled by an H-bonded framework covering most of the SecA structure and allowing conformational alterations with minimal energy inputs. As a result, dimerization, the channel and nucleotides select pre-existing conformations, and alter local dynamics to restrict or promote catalytic activity and clamp motions. These events prime the translocase for high affinity reception of non-folded preprotein clients. Such dynamics nexuses are likely universal and essential in multi-liganded protein machines.

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Krisnamurthy, S., Eleftheriadis, N., Karathanou, K., Smit, J. H., Portaliou, A., Chatzi, K. E., Karamanou, S., Bondar, A.-N., Gouridis, G., Economou, A.. 2021-01-19. A nexus of intrinsic dynamics underlies translocase priming. https://doi.org/10.1101/2021.01.18.427065

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