mPPases create a conserved anionic membrane fingerprint as identified via multi-scale simulations

Abstract

Membrane-integral pyrophosphatases (mPPases) are membrane-bound enzymes responsible for hydrolysing inorganic pyrophosphate and translocating a cation across the membrane. Their function is essential for the infectivity of clinically relevant protozoan parasites and plant maturation. Recent developments have indicated that their mechanism is more complicated than previously thought and that the membrane environment may be important for their function. In this work, we use multiscale molecular dynamics simulations to demonstrate for the first time that mPPases form specific anionic lipid interactions at 4 sites at the distal and interfacial regions of the protein. These interactions are conserved in simulations of the mPPases from Thermotoga maritima, Vigna radiata and Clostridium leptum and characterised by interactions with positive residues on helices 1, 2, 3 and 4 for the distal site, or 9, 10, 13 and 14 for the interfacial site. Due to the importance of these helices in protein stability and function, these lipid interactions may play a crucial role in the mPPase mechanism and enable future structural and functional studies.Author summaryIn this work we have been able to demonstrate conservation of lipid-interaction sites on proteins from distinct species that deviated from their evolutionary common ancestors a long time ago, as in the case of the membrane-integral pyrophosphatases from a thermophilic bacteria species and a plant species studied here. This retention of a common lipid interaction profile or “fingerprint” and our ability to predict this for other proteins in this family may indicate that they are more integral to protein function than previously thought. By identifying lipid interactions that may act to stabilise the protein structure, these properties could be exploited to gain protein structures, and the interfacial site’s potential involvement in inter-subunit communication may be useful for further investigation of the catalytic cycle of this clinically relevant membrane protein family.

Functional and structural asymmetry suggest a unifying principle for catalysis in integral membrane-bound pyrophosphatases

“…global conformational changes should occur in the first 0.1-0.2 s at 20 °C. These need to be tested through functional and structural studies, in particular the use of time-resolved, single-molecule techniques to capture further details of mechanism, as well as efforts to capture mechanistic details through molecular dynamics – efforts that are already underway (Holmes et al, 2022).…”