We had hoped that 2006 would be a calm year for the MX Group, used for consolidation of the work performed during 2005. Of course this has not proven to be the case! During 2006, the MX beamlines welcomed over 2000 visitors carrying out more than 660 separate experimental sessions. Moreover, and as predicted, the availability of sample changing robots has fundamentally altered the way in which the beamlines are used: in the period 1st April to 16th December 2006, the sample changers were used to mount around 13,000 crystals. The availability of sample changers means that users can either screen large numbers of samples before collecting data from the best possible crystal or, in the case of pre-screened samples, collect many datasets very rapidly indeed. Such an intensive use of the beamlines means they must be highly reliable. That they continue to remain so is a tribute to the work of all the members of the MX Group (particularly our technical staff) and the support groups with whom we collaborate. We should not forget that, as well as maintaining the beamlines in an excellent operational state, the MX Group also continues to develop the facilities available - a prototype of an automatic data collection pipeline is in an advanced state and we are taking our first, tentative, steps towards making remote access to the beamlines routine for academic users.

The commissioning of the microfocus beamline ID23-2 allowed us to open the beamline to the MX community in November 2006. Use of this latter facility has required a steep learning curve on the part of beamline staff and external users and highlighted the need for improvements in optical components and beamline usage. Nevertheless, the availability of a microfocus beamline on a routine basis for MX has provided an extremely valuable, currently unique, additional tool for structural biology allowing structure determination from crystals that were previously considered too small to be useful (see the report of Flot and colleagues).

We are also increasing the availability of techniques complementary to X-ray diffraction. In addition to an on-line microspectrophotometer working in the UV-visible range, Raman spectroscopy is now available on the beamlines and allows the on-line monitoring of radiation damage to crystals of biological macromolecules (see McGeehan et al.). This facility will be extended when the move of the “cryo-bench” lab is completed. The relocation will install the laser and spectroscopic tools of the lab into custom facilities situated on ID23. The intention is to provide the community with online access to these tools from both of the endstations of ID23. A workshop will be arranged in early 2007 to further explore the scientific exploitation of these spectroscopic techniques.

Increasingly, structural biologists study systems implicated in research areas such as cancer and drug resistance. This trend is reflected in several of the highlights found in this chapter. Hsp90 (heat shock protein 90) is essential for cell viability in all eukaryotes. The involvement of many Hsp90 client proteins in the development and progression of cancer means that Hsp90 is an exciting potential target for new anti-cancer drugs. The crystal structure analysis of an Hsp90-nucleotide-p23/Sba1 closed chaperone complex (Pearl et al.) provides detailed insight into the conformational biochemistry of the macromolecular systems in which Hsp90 is involved, information which may ultimately help the development of drugs to combat cancer. The ability of bacteria to recombine gene cassettes using integron integrases is an important factor governing their adaptability to changing environmental conditions. The elucidation of the structure of the integron integrase VchIntIa from Vibrio cholerae in complex with a target attC site (MacDonald et al.) provides information on how, at a molecular level, one might try to limit acquired genetic traits such as antibiotic resistance. Escherichia coli strains that have acquired multiple-antibiotic resistance overproduce two proteins: the periplasmic fusion component AcrA and the resistance-nodulation-cell division (RND) type efflux pump AcrB. These interact with the outer membrane protein TolC to transport drugs out of cells. Seeger and colleagues have determined the structure of AcrB as an asymmetric trimer and propose a novel mechanism for the transport of antibiotics. This knowledge may help to understand how to overcome the problem of multiple-antibiotic resistance in bacteria.

The fourth highlight in this chapter (Selmer et al.), is an example of another increasing and encouraging trend that we observe. As well as providing crucial information on how ribosomes interact with release factors at the end of the translation process, the work illustrates how European synchrotron sources can work together to provide the best opportunities for the elucidation of scientifically important macromolecular crystal structures. For the structure described, initially data could only be collected to a resolution of 4.6 Å at the ESRF. However, taking advantage of the sample changers installed at the ESRF, subsequent screening of hundreds of crystals showed that a refinement in crystallisation conditions had produced crystals diffracting to a much higher resolution limit (dmin = 2.8 Å). These crystals were taken to the SLS, where beam time was available, and a full data set collected.

The in-house research highlights concentrate on the role of metal ions in biology. Cuypers et al. describe the crystal structures of two Dps (DNA protecting protein under starved conditions) proteins: Dps1 and Dps2 from Deinococcus radiodurans. The iron storage and DNA binding functions of Dps proteins provide protection for cells during stress, possibly by the inhibition of Fenton chemistry and the suppression of free-radical chemistry. The crystal structures reveal channels in the surface of the proteins that facilitate the transit of iron from solvent to the ferroxidase centres of Dps. In the second example of in-house research, the structure of the nickel regulator, NikR from Helicobacter pylori is presented. This bacterium colonises the human stomach and its presence can lead to severe gastric diseases including stomach cancer. The bacterium’s ability to survive the low pH found in the human stomach is centred on the Ni-dependent enzyme urease. However as nickel can also be toxic at high concentrations, H. pylori has developed a mechanism enabling tight regulation of nickel content, usage and storage that depends on NikR. The structural studies by Dian et al., combined with their biochemical analysis, provide a structural basis for nickel regulation by NikRs.

As well as providing facilities for use by academic researchers, the MX Group beamlines are used for proprietary research, mainly by pharmaceutical companies. Rowland and colleagues, provide an example of the type of research carried out. They describe the crystal structure of the 2D6 isoform of human Cytochrome P450. This structure shows a well-defined cavity above the haem group, explains why three residues, Asp301, Glu216 and Phe120 are important for substrate binding, accounts for published site-directed mutagenesis data and has provided insight into the metabolism of several compounds, including the antihypertension drug debrisoquine.

The final article in this year’s chapter describes progress in obtaining molecular envelopes from macromolecular powder diffraction data (Wright et al.). Despite the advances made in the field of structural biology and the advent of microfocus beamlines dedicated to the technique, some macromolecules may never provide single crystals from which useful diffraction data can be obtained. Although currently a low resolution technique, this article shows that phases produced from powder diffraction experiments can produce accurate molecular masks. Improvements in the technique should lead to higher resolution information being obtainable.

G. Leonard and S. McSweeney