Macromolecular crystallography (MX) provides key information to advance basic research in biology and chemistry. MX drives forward biomedical research by informing on structure-function relationships of proteins and nucleic acids relevant to health, or pharmaceutical development. In the past year, the beamlines at ESRF have continued to support the pharmaceutical industry, helping them to carry out their research. The community sees little of this research but it remains nevertheless an important ESRF activity.

What the research community does see is the impressive output of publications, seminars or lectures founded on ESRF generated results. It is increasingly difficult to identify only a few highlights because of the high level of activity in structural biology in Europe for many important areas of biology. The increased efficiency and automation of synchrotron data collection at the ESRF are a major driving force in structural biology and certainly key in ensuring that European MX research remains internationally competitive. This is brought home in particular to the MX-Beamtime Allocation Panel (BTAP) review committee who see the results from the user community, and the publication lists including all of the top science journals, general and specialised. The success presents the MX-BTAP and the ESRF with a challenge. The continued growth of the structural biology community, oversubscription of beamlines and the need to continually update and improve facilities has placed a strain on the allocation of resources and it is a difficult juggling act to ensure researchers get beamtime sufficient for their needs. The user community has a duty here to help, and the efficiency of the BAG system might usefully be exploited by more laboratories.

That aside, now for some highlights. Success throughout Europe in the past year is impressive and we could fill this entire report solely with structural biology. Space restrictions mean we only present a subjective snapshot of ESRF research and we include examples from both the ESRF external and the in-house research programmes.

Irregularities in phosphotinositade 3-kinases occur frequently in many cancers, Miled et al. present a model for the structure of one such kinase - PI3K - in complex with a partner molecule. This complex reveals the location of the cancer inducing mutations and allows a description for the consequences of these mutations to be proposed. Niemann et al. have resolved the crystal structures of the bacterial surface protein InIB and the activating kinase Met, this complex initiates cell invasion in the human pathogen Listeria monocytogenes. The crystal structure reveals an unexpected region of contact between the partner proteins – an interaction which appears to be essential for activation of Met, presumably via a stable structural reorganisation upon complex formation. On a similar theme the entry of viruses into their hosts requires the virus to bind to one or more receptors on the host cell surface; fusion of the virus and host membrane follows. Vesticular stomatis virus (VSV) contains a single transmembrane glycoprotein that is responsible for both receptor recognition and membrane fusion. Roche et al. present the structure of this protein, VSV G, in different states. The ensemble of models reveals the spectacular structural rearrangements that the protein undergoes in order to perform its functions.

The influenza virus remains a potent risk to human health. A search for an effective treatment has focussed on understanding the function of the polymerase responsible for transcription and replication of the viruses RNA genome. Using a novel technological approach Tarendeau et al. identified an unsuspected domain at the C-terminus, this domain plays a role in the localisation of the polymerase and offers some ideas for the mechanisms of transfer of influenza viruses to humans. Also using novel technology of a completely different form, Katona et al. deployed Raman spectroscopy to provide new data to elucidate the mechanism of Fe-superoxide reductase. The iron provides the oxidative centre in the enzyme and the Raman spectroscopy experiments allowed the reaction intermediates to be resolved and a reaction mechanism proposed.

Homologous recombination of DNA plays an important role in genetic diversification and the repair of DNA lesions. Bacteria employ a number of mechanisms to effect this action, and employ two major protein complexes: RecBCD (ESRF Highlights 2005) and RecFOR. Timmins et al. have determined the structure of the complex formed between RecR and RecO and proposed a model for the supercomplex that would be assembled as the RecRO complex binds to damaged DNA. Recombination and rearrangement of DNA is a ubiquitous biological activity and the key step is the formation of a four-way DNA junction – a Holliday junction. Hadden et al., determined the structure of a Holliday junction in complex with the protein partners necessary for resolving the junction. Their structure was the result of extensive screening for crystallisation and made significant use of the microfocus capabilities of the ESRF MX beamlines. The structure reveals a complex suggestive of extensive structural changes employed to ensure successful organisation of the DNA.

The cellular response to stress is a vital component of adaptation to environmental change for prokaryotic and eukaryotic cells. The signalling pathways that have evolved are sophisticated and require precise temporal regulation to maintain cell viability. MAPK kinases are responsible for the transduction and amplification of signals via phosphorylation. The MKP family of proteins dephosphorylate and deactivate MAPK kinases. In an apparent contradiction MKPs contain a catalytic cysteine sulphydryl group that is sensitive to oxidation. Thus one may expect that, under conditions of oxidative stress, MKPs would become oxidised and loose the ability to regulate MAPKs. To investigate the way in which Nature has handled this dilemma, Fox et al. studied an MKP under both oxidising and reducing conditions revealing the mechanism by which this family maintains activity under conditions of oxidative stress.

Drugs targeting the integral membrane protein leukotriene C4 synthase (LTC4S) are important targets for treatment of asthma. The structure of LTC4S was determined by Martinez Molina et al. and revealed a protein that despite its relatively small size is able to recognise substrates with widely different chemical properties and which plays a crucial role in delivering these substrates to a lipid for conjugation. Translocation of proteins across membranes is a cellular function that is conserved throughout the kingdoms of life. A variety of mechanisms to perform this function are employed in Nature, including the two partner secretion system (TPS), which secrete large proteins that may serve as virulence factors. The structure of the transporter that secretes the Bordetella pertussis adhesion filatementous hemaglutanin, reveals a dynamic pore protein and allowed Clantin et al. to propose a mechanism of action.

The highlights reveal a number of elements shared with other projects not included here. Many projects required extensive screening, often requiring many hundred of crystals to be analysed and efficient automation is essential for success. The relatively low resolution of diffraction in some projects requires optimisation of experiments and the use of microbeams is mandatory. Projects require access to multiple complementary beamlines so each aspect of the structure determination process and the biological interpretation can be optimised. These themes are addressed in the proposals for the upgraded ESRF and maintenance of the ESRF’s successful user programme will require careful organisation and optimisation of MX resources.

W.N. Hunter (University of Dundee, UK) and S. McSweeney