abstracts
Riboflavin synthase (RS) catalyzes the last step of riboflavin biosynthesis in microorganisms and plants, which corresponds to the dismutation of two molecules of 6,7-dimethyl-8-ribityllumazine to yield one molecule of riboflavin and one molecule of 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione [1]. Due to the absence of this enzyme in animals and the fact that most pathogenic bacteria show a strict dependence on riboflavin biosynthesis, RS has been proposed as a potential target for antimicrobial drug development. Eubacterial, fungal and plant RSs assemble as homotrimers lacking C3-symmetry [2]. Every monomer can bind two substrate molecules, yet there is only one active site for the whole enzyme, which is located at the interface between two neighboring chains. This work reports the crystallographic structure of RS from the pathogenic bacterium Brucella abortus (the etiological agent of the disease brucellosis) in its apo form, in complex with riboflavin, and in complex with two different product analogues, being the first time in which an intact RS trimer is solved with bound ligands. These crystal models support the hypothesis for an enhanced flexibility in the particle and also highlight the role of the ligands in assembling the unique active site. Kinetic and binding studies were also performed to complement these findings. The structural and biochemical information generated may be useful for the rational design of novel RS inhibitors with antimicrobial activity.
abstracts
"PROXIMA 1, a beamline for macro-molecular crystallography at the 3rd generation synchrotron source SOLEIL, is equipped with a multi-circle goniometer (alpha 50 degrees) as well as a PILATUS 6M detector. These features, along with the extended energy range of the beam line towards the low energies (down to 5.5 keV) and the possibility to adapt the source size to the sample in order to optimize signal to noise ratio, have made the beam line very attractive for S-SAD phasing with more than seven examples of successful de novo phasing achieved over the last two years. The use of low energies has also proved a significant aid in assisting with MODEL building. The technical capabilities of the beam line for low energy data collections will be presented, along with a number of examples of the successful use of low wavelengths on the beam line. The importance of combining data from multiple sample orientations in order to achieve ""true multiplicity"" will be highlighted, as well as the importance of combining data from multiple crystals in order to achieve high multiplicity."
Keywords: S-SAD.
abstracts
To celebrate the International Year of Crystallography 2014, the Argentinian Crystallography Association ("Asociación Argentina de Cristalografía", AACr) [1] has launched the Crystal Growing Competition to be held June-October 2014 among Argentinean high school students. This activity is sponsored by the IUCr, CONICET (Argentinean Science Council) and MinCyT (Argentinean Ministry of Science, Innovation and Technology). Based on IUCr suggestion [2] and successful previous experiences in other countries [3], we planned the program of the activity. Before the contest, a five hours course including the basic concepts of crystal growing and crystallization experiences demonstrations will be offer for the teachers of the interested schools. They will take place at different regions of the country during April. The information of the contest together with the instructions on how to grow crystals and guidelines for the teachers will be provided on the web. After the students sign up, they will growth their crystals and create a slideshow presentation or a video to show their work to the evaluation committee before the end of August 2014. Winners will be announced on September 15th, they will be invited to show their work at the X Annual Meeting of the Argentinean Crystallographic Association, Mar del Plata, Argentine, 28-31 October 2014. A special session will be held as a satellite activity of the meeting on October 27th and the awards ceremony of the Crystal Growing Competition will be during the opening ceremony. Besides this, everyone participating of the Argentinean contest has a chance to compete in the International Crystal Growing Competition. Trough this exciting, funny and hands-on scientific experience, crystallography and other related scientific fields will be promoted along the high school community across the country being also, a way to encourage youth to continue exploring science and developing their scientific skills.
abstracts
"The history of Crystallography in Argentina is very rich, probably starting with the pioneer work of Prof. Ernesto Galloni in the decade of the `40s. Thanks to Prof. Galloni, the National Committee of Crystallography was founded in 1958 and recognized by the IUCr in 1960. This committee organized several scientific meetings and was in good contact with the Ibero American Crystallography Group during about 35 years. After some crisis in the late `90s, some young crystallographers decided to reorganize the activities and form the Argentinian Association of Crystallography (AACr), which was finally founded on October 30th, 2004, on the occasion of the ""National Workshop on Crystallography"" held in Villa Giardino, Province of Córdoba. Therefore, in the International Year of Crystallography, the AACr is also celebrating its tenth anniversary. The regular annual events of the AACr are a scientific meeting, a school on Crystallography and a workshop. This year, they will be held in Mar del Plata (Province of Buenos Aires) in the period of October 27th-Novembre 7th. In addition, many other academic activities such workshops or postgraduate courses are being organized in the whole country. It is worth to remark the School on Fundamental Crystallography to be held in La Plata, followed by an Agilent-UNESCO-IUCr OpenLab in La Plata and Buenos Aires, in April-May. Moreover, taking into account that Crystallography is a field that needs more promotion in our country, the AACr decided to propitiate several educational and dissemination activities. They include a national crystal growing contest, promotion of Crystallography in high and primary schools through the National Fairs of Science of the Ministry of Education, dissemination talks for different audiences, exhibitions, etc. Acknowledgements: The AACr thanks all the crystallographers that are working hard in these activities: G. Echeverría, O. Piro, S. Suárez, M. Saleta, D. Tobía, R. Carbonio, G. Aurelio, J. Pedregosa, F. Doctorovich, S. Conconi, L. Baqué, F. Napolitano, S. Alconchel, C. Alvarez, A. Ares, C. Bernini, S. Brühl, M. Dailoff, M.A. Foi, M. Harvey, M.S. Lassa, S. Montoro, E. Pannunzio Miner, etc."