Abstract
ConspectusProtein crystallography represents at present the most productive and most widely used method to obtain structural information on target proteins and protein–ligand complexes within the atomic resolution range. The knowledge obtained in this way is essential for understanding the biology, chemistry, and biochemistry of proteins and their functions but also for the development of compounds of high pharmacological and medicinal interest. Here, we address the very central problem in protein crystallography: the unpredictability of the crystallization process. Obtaining protein crystals that diffract to high resolutions represents the essential step to perform any structural study by X-ray crystallography; however, this method still depends basically on trial and error making it a very time- and resource-consuming process. The use of additives is an established process to enable or improve the crystallization of proteins in order to obtain high quality crystals. Therefore, a more universal additive addressing a wider range of proteins is desirable as it would represent a huge advance in protein crystallography and at the same time drastically impact multiple research fields. This in turn could add an overall benefit for the entire society as it profits from the faster development of novel or improved drugs and from a deeper understanding of biological, biochemical, and pharmacological phenomena.With this aim in view, we have tested several compounds belonging to the emerging class of polyoxometalates (POMs) for their suitability as crystallization additives and revealed that the tellurium-centered Anderson–Evans polyoxotungstate [TeW6O24]6– (TEW) was the most suitable POM-archetype. After its first successful application as a crystallization additive, we repeatedly reported on TEW’s positive effects on the crystallization behavior of proteins with a particular focus on the protein–TEW interactions. As electrostatic interactions are the main force for TEW binding to proteins, TEW with its highly negative charge addresses in principle all proteins possessing positively charged patches. Furthermore, due to its high structural and chemical diversity, TEW exhibits major advantages over some commonly used crystallization additives. Therefore, we summarized all features of TEW, which are beneficial for protein crystallization, and present ten good reasons to promote the use of TEW in protein crystallography as a powerful additive. Our results demonstrate that TEW is a compound that is, in many respects, predestined as a crystallization additive. We assume that many crystallographers and especially researchers, who are not experts in this field but willing to crystallize their structurally unknown target protein, could benefit from the use of TEW as it is able to promote both the crystallization process itself and the subsequent structure elucidation by providing valuable anomalous signals, which are helpful for the phasing step.
Highlights
Biological macromolecules are essential for the myriad of biological functions of all living organisms
As the properties and functions of macromolecules can be derived from their 3D structure, macromolecular structure determination has gained immense importance, especially for research fields working on pharmaceutical and medicinal issues
TEW led to the crystallization of two hitherto structurally unknown proteins, mushroom tyrosinase[4] from Agaricus bisporus[5−7] and aurone synthase[8−11] from Coreopsis grandif lora,[12−14] and the model protein hen-egg white lysozyme (HEWL) into a previously unknown crystal form.[15]
Summary
One of the easiest attempts to improve the crystallization probability of a macromolecule is the application of so-called additives. Additives are small compounds or molecules that are able to interact with the protein in a crystal assembly promoting manner and can exhibit dramatic influence on the crystallization process. As they are able to induce more stable or favorable conformations that are in turn mostly more likely to crystallize than the ligand-free form of the protein.[2] These additives are, proteinspecific and merely restrictedly applicable. Other additives like charged groups or molecules or ions are able to promote crystallization by providing intermolecular, noncovalent crosslinks of electrostatic nature between protein molecules but it is mostly impossible to predict which compound under which conditions will lead to such beneficial interactions. An universal additive with a rich repertoire of crystal packing affecting properties and addressing a larger group of macromolecules would be a groundbreaking advance in protein crystallography including all research disciplines relying on structural input
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
