We are studying the structure and molecular mechanisms of biological rotary motors. Our current focus is on rotary A-type ATPases, which synthesise ATP in archaea and in certain eubacteria [1]. Another project involves components of the bacterial flagellar motor that propels bacteria through viscous media [2]. Both systems represent transmembrane multiprotein assemblies that convert energy in form of trans-membrane proton or sodium gradients into mechanical work in form of torque. Our aim is to understand common principles of proton-powered biological motors in molecular detail.

In both cases we use 3D reconstructions derived from electron micrographs of the intact complexes as low-resolution envelopes to fit higher resolution X-ray structures of individual subunits. This has allowed us to derive composite “atomic” models of the intact complexes. In addition we have obtained structures of individual components in different conformations. Supported by molecular dynamics simulations this has allowed us to obtain not only static 3D snapshots, but also information about the dynamics of these biological machines [3, 4]. I will talk about the most recent results on ATP synthases and flagellar motor structures and how complementary techniques help us to understand the physiological roles of these systems.

References:

[1] Stewart AG, Sobti M, Harvey RP, Stock D (2013) “Rotary ATPases: Models, machine elements and technical specifications” BioArchitecture 3. Epub ahead of print.

[2] Stock D, Namba K, Lee  LK (2012) “Nanorotors and self-assembling macromolecular machines: the torque ring of the bacterial flagellar motor” Current Opinion in Biotechnology 23, 545-54.

[3] Stewart AG, Lee LK, Donohoe M, Chaston JJ, Stock D (2012) “The Dynamic Stator Stalk of Rotary ATPases” Nature Communications 3, 687.

[4] Lee LK, Ginsburg MA, Donohoe M, Crovace C, Stock D (2010) “Structure of the torque ring of the flagellar motor and the molecular basis for rotational switching” Nature 466, 996-1000.