From an analysis of the sodium-transporting vacuolar ATPases (V-ATPases) of the bacterium Enterococcus hirae, Takeshi Murata of the RIKEN Systems and Structural Biology Center, Yokohama, and colleagues recently obtained valuable structural and functional information about a process that pumps protons and other positively charged ions across cellular membranes1.
Figure 1: The crystal structure of the E. hirae V-ATPase with molecules of DCCD (green spheres) bound to E139 at each individual subunit.
Copyright : 2011 Takeshi Murata
Adenosine triphosphate (ATP) is the primary energy ‘currency’ within cells, and numerous enzymes are powered by the metabolic processing of this molecule via a mechanism known as hydrolysis. V-ATPases can exploit this process to pump positively charged ions across cellular membranes. This process occurs at the junction between a rotating ‘K’ domain and a fixed ‘a’ domain within the segment of the protein that resides at the cell membrane, although the specifics remain unclear.
N,N’-dicyclohexylcarbodiimide (DCCD), a chemical that selectively reacts with a specific glutamate amino acid (E139) within the sodium-binding pockets of the K ring, proved valuable in assessing this protein’s function. The researchers demonstrated that DCCD inhibited sodium binding by nearly 30-fold, but that this inhibition was sharply reduced when the enzyme was pretreated with sodium ions, suggesting that the two molecules interact with overlapping targets within the ring.
The K ring is composed of ten identical subunits, and DCCD efficiently reacts with E139 in each of these individual components (Fig. 1). By gathering structural data from the DCCD-treated V-ATPase, Murata and colleagues obtained a snapshot of what the protein looks like in the absence of sodium, which they could in turn compare against the structure of the sodium-bound form.
Although the two structures were largely similar, DCCD treatment triggered a change in E139 that locked the sodium binding sites into an ‘open’ structure that prevented ion retention. The negative charge of E139 made an important contribution to the binding of the positively charged Na+ ion; DCCD appeared to work by neutralizing this charge. The researchers hypothesize that a similar process governs ion release during the transport process; as the K domain rotates, each subunit’s E139 interacts with a positively charged amino acid on the domain, triggering ion release and transfer across the membrane.
Confirming this model will require additional structural data. “We would like to obtain the structure of [the] whole complex containing both the rotor ring and a-subunit,” Murata says. Nevertheless, these findings could prove immediately applicable to the development of more effective ATPase inhibitors, a class of drugs potentially useful for treating cancer and other diseases. “V-ATPases are of considerable pharmacological interest,” says Murata.
The corresponding author for this highlight is based at the Systems and Structural Biology Team, RIKEN Systems and Structural Biology Center
When Air is in Short Supply - Shedding light on plant stress reactions when oxygen runs short
23.03.2017 | Institut für Pflanzenbiochemie
WPI team grows heart tissue on spinach leaves
23.03.2017 | Worcester Polytechnic Institute
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
23.03.2017 | Life Sciences
23.03.2017 | Power and Electrical Engineering
23.03.2017 | Earth Sciences