Structure of the revealed nanoturbine protein



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Structure of the revealed protein nano turbine

Each protein subunit is of different color. The V1 domain is at the top, Vo at the bottom, the peripheral rods are left and right. The background shows a wind pump. Credit: IST Austria, 2019

Cells use protein complexes known as ATP synthases or ATPases for their energy needs. Adenosine triphosphate (ATP) molecules supply most of the processes that support life. Professor Leonid Sazanov, a structural biologist, and his research group at the Institute of Science and Technology of Austria (IST Austria) in Klosterneuburg, Austria, determined the first atomic structure of the representative of the V / A-ATPase family, thus filling the empty evolutionary tree of these essential molecular machines. These results obtained using the latest cryoelectronic microscopy methods revealed a structure similar to that of the enzyme in a water or turbine mill. They were published in the journal Science.


Rotating power

ATP synthases / ATPases are large membrane protein complexes that share global building planes and rotational catalysis mechanisms. This family of proteins includes F-type enzymes found in mitochondria (cell production plants), chloroplasts (organelles that photosynthesize in plants) and bacteria; Type V (vacuolar) found in intracellular compartments in eukaryotes (higher organisms with a nucleus) and type A (Archean) in prokaryotes – archaea (old microorganisms) and some bacteria.

Different aromas of ATPases

F and A type enzymes generally produce ATP, which is driven by proton flux through the membrane. Type V enzymes generally work in the opposite direction, using ATP to pump protons. The V- and A-ATPases have a similar structure but differ from the F type by having two or three peripheral rods and additional protein subunits connecting V1 and Vo. Type V enzymes have probably evolved from type A and, because of these similarities, type A is also called V / A-ATPase. Some bacteria, including Thermus thermophilus, acquired a type A enzyme. Long Zhou, a postdoctoral fellow in the Sazanov research group of IST Austria, purified and studied this enzyme (ThV1Vo) by cryo-EM. Unlike type F, for type V ATPases, only isolated V1 and V domain structures were determined previously. The coupling of V1 to Vo was therefore not known and knowledge of the complete catalytic cycle was lacking.

Structure of the revealed protein nano turbine

Each protein subunit is of different color. The V1 domain is at the top, Vo at the bottom, the peripheral rods are left and right. The background shows a crude cryo-EM micrograph, with individual visible ATPase molecules. Credit: IST Austria, 2019

Plasticity and competition

Scientists have determined not one, but a total of five structures of the entire ThV1Vo enzyme, using the recently developed cryo-electron microscopy methods as part of the "resolution revolution" of this technical. The structures represent several conformational states of the enzyme differing by the position of the rotor inside the stator. The overall conformational plasticity of ThV1Vo is revealed by a substantial V1 oscillation in the transition space from one state to another. This is the result of a mechanical competition between the rotation of the folded central rotor and the stiffness of the stator. The V1-Vo coupling is obtained by a narrow structural and electrostatic fit between the tree and the specific V-type subunit connecting it to the C-ring. Visualization of the proton path revealed significant differences in the distribution charged protein residues over that of F-ATPases, with a tighter "checkpoint" preventing the "slipping" of the enzyme.

Why additional complexity?

Instead of a single peripheral rod of F-type enzymes, A-types such as ThV1Vo have two peripheral stems, while eukaryotic V-types have three. But what is the benefit of the extra complexity of already very large protein assembly, as well as additional subunits connecting V1 and Vo? The F1 / V1 domain has triple symmetry and so an ATP molecule is produced (or consumed) for every 120 ° rotation of the stator inside F1 / V1. Professor Leonid Sazanov said: "In V / A-ATPase solutions, this step is a single rotation of 120 °, unlike the F-ATP synthase where it is divided into several substeps.Thus, greater plasticity may be required in ThV1Vo to link these steps from 120 ° in V1 to smaller steps per subunit in the Vo ring c12.This additional flexibility can be offered in V types by additional device stems and the sub-units of connection Our new structures show how this is done, providing a framework for the whole V-ATPase family ".


Another piece of the ion pump puzzle


More information:
"Structure and conformational plasticity of the intact Thermus thermophilus ATPase type V / A " Science (2019). science.sciencemag.org/cgi/doi… 1126 / science.aaw9144

Provided by
Institute of Science and Technology of Austria

Quote:
Structure of the revealed nanoturbine protein (August 22, 2019)
recovered on August 22, 2019
at https://phys.org/news/2019-08-protein-nanoturbine-revealed.html

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