Inferring subsystem efficiencies in bipartite molecular machines

Molecular machines transduce energy between different forms in order to accomplish innumerable tasks within living organisms. Many of these machines are composed of two coupled subsystems, like F0F1-ATP synthase or a transport motor pulling a diffusive cargo. While subsystem efficiencies of these molecular machines have been measured in isolation, less is known about how they behave when coupled together and acting in concert. In this work we derive upper and lower bounds on the subsystem efficiencies of individual components of a bipartite molecular machine. Our results are well-suited to infer these subsystem efficiencies from limited experimental data. We demonstrate their utility by estimating the efficiencies of the F0 and F1 subsystems, as well as that of a kinesin motor while it pulls a diffusive cargo.