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Science: Phosphate Balance in Higher Organisms elucidated
12 May 2009
Polyphosphate chains play an important physiological role in many organisms, for example to ensure cell growth even under deficiency conditions. To date, there is however little data available on their formation and mode of function. Chemists and biochemists at the Ruhr University, working in collaboration with research scientists at the European Molecular Biology Laboratory in Heidelberg and the University of Lausanne, have now gained insight into the basic data on the formation mechanism of polyphosphate chains. The scientists have been able to identify the first x-ray structure of the enzyme responsible for the biosynthesis of polyphosphates in highly developed organisms (eukaryotes) and to distinguish the basic biochemical processes. The molecular catalytic processes can be accurately described based on the data obtained. This knowledge constitutes the foundation for further targeted research into the role of polyphosphates. The scientists have published their results in the current edition of the Science Journal.
Characterization is a milestone
The enzyme investigated - VTC (vacuolar transporter chaperone) - makes use of the universal “energy carrier” ATP (adenosine triphosphate) within cells for the gradual synthesis of phosphate chains. A depot, which the organism can resort to under stress conditions, is thus created. Using structure-biological and biophysical methods, the scientists were able to show which molecular tools the enzyme uses for the reorganization of the phosphates from the source into the depot. Prof. Christian Herrmann (Physical Chemistry I) explained that the structure of the chain-shaped depot substance and its simultaneous transport in a cellular subunit with the aid of a tunnel-shaped protein structure is of particular interest. The VTC enzyme is part of a large protein complex that reaches the cell via an inner membrane. Its characterization is a milestone for research into ATP-dependent membrane processes.
Proteins: a focal point of research at RUB
Intense research into proteins has been ongoing at the Ruhr University during the past few years. This is particularly evident in the successful continuation of the Collaborative Research Centre (Sonderforschungsbereich) 642 (“ATP and GTP-dependent Membrane Processes”) and the establishment of the Protein Research Department. The excellent state-of-art experimental equipment and the expertise of the experienced scientists form the foundation stone for highly efficient research into and prompt solving of the problems of modern Life Sciences within the international highly competitive research environment. Prof. Herrmann underscores that, in this connection, it is particularly pleasing that the biochemistry scholarship holder Mark Wehner from RUB’s Research School was responsible for a significant contribution from the Bochum team. This confirms the concept of fostering young academics within the frameworks of the Excellence Initiative.
Structural model of the VTC4p* in a complex with a polyphosphate chain which has been synthesized from ATP. The surface of the protein is presented as transparent; the secondary structural elements in the interior are presented as band structure. The ATP, as phosphate source, bonds to the site on the enzyme designated with the asterisk. Linear polyphosphates are formed through a tunnel-shaped opening in the protein.