The year 2003 was one of great excitement and hard work at the Macromolecular Crystallography (MX) beamlines of the ESRF (ID14 A&B, ID29), and the year's closing brings about a welcome chance to report on some of the work carried out there. Scientifically a large number of interesting crystal structures were produced, and a flavour of these is given in the choice of highlights presented here.

During the year, more than 2000 visitors came to perform experiments at the MX beamlines with, on average, visitors using 24 hours of beamtime per visit. In all, around 500 distinct experimental sessions were scheduled. This high throughput of visits could not be sustained without the excellent support provided by the User and Travel offices, Experiments Division secretariat and the ESRF Support Groups and Services. The MX group itself functions as an effective and highly-dedicated team providing excellent operational support as well as spearheading technical improvements to the beamlines.

The Partnership for Structural Biology (PSB), has continued to develop. In particular the plans for the dedicated laboratory space have progressed to the extent that planning permission has been obtained. Ground break for the new building is expected for April 2004 with about 12-month build time. The related project, the construction of the 2 end-stations on ID23 has reached the conclusion of the first part the adventure with the commissioning of the end-station ID23-1. Test experiments indicate that the beam-line will provide good quality diffraction data and that it operates well in the energy range

5 - 20 keV. User access to the end-station will begin in April 2004. Construction of the second end-station (ID23-2) will continue during 2004. This facility will operate at fixed energy (14.2 keV) and the aim is for a focal spot size of ~ 10 µm2. We expect to be finalising commissioning for this part of ID23 during the latter part of year and early 2005.

The automation of the MX beamlines continues in earnest. At the ESRF we view automation as a pipeline involving the following processes: automatic beam delivery, characterisation and optimisation; sample delivery (changing and centering); experimental design; data analysis and post processing. A team comprising staff from both the ESRF and the EMBL Grenoble outstation has been formed which will address these issues and support for this initiative will be provided via the EU project grants SPINE and bioXhit. The year 2003 has seen the installation of many of the components necessary for the operation of our "pipeline" and a summary of progress in this regard is given in the following article by J. McCarthy and B. Shepard on behalf of all of those involved. The report covers the automatic provision of focussed beam on ID29; the installation of improved optical visualisation systems; the ESRF/EMBL sample changer which is now installed on ID14-3; steps towards automatic experimental design for both single and multiple wavelength experiments.

The External Scientific Programme has seen an increased tendency towards the study of the structures of macromolecular complexes, several of which are presented here. Nelson et al. report the structure of photosystem I from a higher plant (pea). This multi-subunit transmembrane protein complex has a molecular weight of ~ 540 kDa and represents one of the largest assemblies solved by macromolecular crystallography. The structure, and in particular the arrangement of chlorophylls around the reaction centre, provides significant insight into the mechanism of solar energy conversion in plants. An understanding of the mechanistic forces driving muscle movement is underpinned by studies of the interactions between myosin and actin. Houdusse and collaborators report the structure of the Rigor State of myosin as determined to 2.0 Å resolution using data collected on ID29. This reveals the structural rearrangement necessary in order to effect the force generating state of myosin. In some cancerous tumors it appears that the over-expression of the tumor suppressor pRb is unfavorable to clinical treatment. The work of Gamblin and colleagues sheds some light on why this may be so. Their structure of the complex formed between pRb and a peptide fragment representing the core pRb-binding domain of the transcription factor E2f also reveals interactions which may aid the design of molecules that might help improve the efficiency of current treatments for a number of cancers.

Of the visitors to the ESRF MX beamlines, about 20% carried out industrially-related activities. Such use of the MX beamlines continues to grow steadily and, in addition to the sale of beamtime, the ESRF now offers the possibility of 'mail-in' data collection via the MXpress service. A typical example of the work carried out by industrial users of the facility is that reported here by Astex Technology. This details the structure of Cytochrome P450 in complex with S-warfarin, and may help to provide a structural basis for the occurrence of in vivo drug-drug interactions.

In addition to providing beam-time through national institutions, the CRG beamlines BM30 and BM14 also provide significant amounts of beam-time for use in the External Scientific Programme of the ESRF. The tunable nature of these beam-lines means they are ideally suited to the exploitation of anomalous scattering in MX and beam-time allocated here helps to alleviate the significant over-demand for beam-time on the ESRF's dedicated MAD beam-lines ID14-4 & ID29. The quality of the science achievable on these beamlines is demonstrated by two articles in this chapter. Acharya and colleagues describe the structure of human Angiotensin1 Coverting Enzyme (ACE) that may allow the rational design of a new generation of ACE inhibitors for use in the treatment of cardiovascular diseases. The structure of the hepititus C Virus core antigen is described by Menez et al..

The in-house research of the MX group continues to develop and is based on three fundamental elements: methods development; collaboration with external groups and the development of in-house molecular & structural biology skills. Examples from all three of these elements are represented here.

Methodological developments have always represented a major part of the ESRF's MX in-house research interests. Collaborations between ESRF and EMBL Grenoble outstation scientists were the first to produce systematic studies of the effect of high intensity X-rays on biomolecules. This work led to several major breakthroughs in our understanding of the structural changes caused in crystals by radiation damage. Continuing this work, careful studies by Ravelli and collaborators have identified the possibility of exploiting these structural changes to enhance the phasing opportunities in the use of 3rd generation SR sources. Perhaps in the future radiation damage will no longer be viewed as only an obstacle to structure determination.

The structure of CDP-ME Kinase by Hunter and colleagues represents some of the fruit of a long standing collaboration between ESRF and the University of Dundee. Development of new antibiotic agents presents a major challenge to the pharmaceutical community and there is a continuous search for possible new drug targets. CDP-ME kinase represents a potential new target and its structure determination may pave the way for the development of a new class of antibiotics.

As part of an effort to enhance the platforms for both molecular & structural biology available at the ESRF, the MX group has undertaken a pilot structural genomics project with an emphasis on the radiation resistant bacterium D.radiodurans. This project has so far lead to the cloning of > 100 targets. Extended analysis of ~ 30 of the cloned proteins (Hall and collaborators) has produced pure protein for 21 of the targets. 10 of these have been crystallised and 6 crystal structures have thus far been produced. The proteome of the organism is also being investigated as a function of radiation dose in order to refine the search for further targets for structural investigation.

The scientific exploitation of the MX beamlines continues to flourish, when the technical advancements foreseen for 2004 are in place we expect that the MX community will be able to perform more and more difficult experiments whilst still focusing on their underlying biological goals.

G. Leonard and S. McSweeney