The role of monovalent cations in the ATPase reaction of DNA gyrase.

Four new crystal structures of the ATPase domain of the GyrB subunit of Escherichia coli DNA gyrase have been determined. One of these, solved in the presence of K(+), is the highest resolution structure reported so far for this domain and, in conjunction with the three other structures, reveals new insights into the function of this domain. Evidence is provided for the existence of two monovalent cation-binding sites: site 1, which preferentially binds a K(+) ion that interacts directly with the α-phosphate of ATP, and site 2, which preferentially binds an Na(+) ion and the functional significance of which is not clear. The crystallographic data are corroborated by ATPase data, and the structures are compared with those of homologues to investigate the broader conservation of these sites.

The benefit of the European User Community from transnational access to national radiation facilities.

Transnational access (TNA) to national radiation sources is presently provided via programmes of the European Commission by BIOSTRUCT-X and CALIPSO with a major benefit for scientists from European countries. Entirely based on scientific merit, TNA allows all European scientists to realise synchrotron radiation experiments for addressing the Societal Challenges promoted in HORIZON2020. In addition, by TNA all European users directly take part in the development of the research infrastructure of facilities. The mutual interconnection of users and facilities is a strong prerequisite for future development of the research infrastructure of photon science. Taking into account the present programme structure of HORIZON2020, the European Synchrotron User Organization (ESUO) sees considerable dangers for the continuation of this successful collaboration in the future.