Pioneering new beamline enables discovery of challenging protein structure linked with malaria and cancer

Scientists end 2-year-long struggle to unpick atomic protein structure using Diamond’s I23 beamline

The I23 beamline team
The I23 beamline team
Scientists have cracked a puzzle they have been trying to solve for over two years thanks to the pioneering capabilities on Diamond’s new I23 beamline.
 
The group from St Andrew’s University were trying to determine the atomic structure of an oxidase protein from a family of peptides that have been linked to antimalarial and antitumor activity.
 
Unpicking the structure of the protein could be a very early step towards identifying potential new drug targets for medicines that prevent the spread of malaria and cancer. However no proteins of this type had ever been successfully solved in the past, and the process of finding the structure proved to be a real challenge.
 
The group attempted a number of different methods using techniques available in their university laboratories and other synchrotron beamlines, but they found that the quality of their data was not sufficient to determine the protein’s atomic structure. And so they opted to attempt the experiment using Diamond’s new I23 beamline, which offers advanced long-wavelength macromolecular crystallography. Tuning the wavelength in this way increases the contrast needed to directly solve the protein structure without additional modifications based on the intrinsic information arising from sulphur present in proteins. This technique proved the key to unlocking the elusive structure.
 
The St Andrews group entered into a collaboration with Diamond scientists, including principal beamline scientist Dr Armin Wagner and his team.
Dr Wagner explained why this structure was particularly challenging to solve: “The quality of protein crystals varied significantly from crystal to crystal and the best diffraction data obtained yielded only moderate resolution. In combination with the low sulphur content tuning the wavelength into the long-wavelength range allowed us to increase the phasing information and solve this challenging structure.”
But the process was by no means simple – and the contribution of the synchrotron specialists ultimately proved to be vital.
Prof Jim Naismith, Professor of Chemical Biology, led the research. He said: “Buoyed by promising initial results the group worked late into the night, adopting different strategies in an attempt to maximise the resolution of the data set. The following morning was much the same, but unfortunately during the visit, we were unable to collect a dataset of sufficient resolution to solve the structure - although this was not for lack of trying”.
 
However the I23 team pressed on in trying to unpick the structure. And after a great deal of effort, they were successful.
 
“Thanks to the dedication of the staff at I23 we have now solved a structure we have been trying to solve for over two years”, said Prof Naismith.
Dr Wagner added: “This is a major milestone for the long-wavelength MX Beamline I23. After several years of designing and commissioning, overcoming of technical hurdles, this finally shows the huge potential of this unique facility. Further improvements over the next months will be needed towards routine user experiments, but this first successful structure determination indicates that this novel Beamline will be a key asset in Diamond, helping users to tackle very difficult protein structures."
Prof Naismith and the St Andrew’s team will now use the structure to focus on understanding the regioselectivity of this important biosynthetic enzyme. Putting this enzyme to work will help in the synthesis of novel drug like molecules that currently elude synthetic chemists.