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De novo design of Lanthanide coiled coils for asymmetric catalysis

Periodic Reporting for period 1 - ChiralCatLnCoils (De novo design of Lanthanide coiled coils for asymmetric catalysis)

Reporting period: 2015-09-01 to 2017-08-31

Many biological activities are mediated by specific proteins or enzymes, which usually require metal ions for function. Enzyme-bound metal ions provide binding sites for the natural substrates and function as catalytic centers. This has motivated several attempts to reproduce, at least partially; the catalytic function of metalloenzymes, using metal bound coiled coil CC peptide complexes as models. The design and development of transition metal binding artificial peptides having specific chemical functions and/or interesting physical properties may offer exciting opportunities to advance modern science including medicine. However, this aim not only demands the ability to develop new protein structures capable of coordinating specific transition metal ions, but also requires insight into how their properties can be influenced by the interplay between coordination chemistry and the protein environment. In light of this dispute, a large majority of de novo (from first principles) Metallo Coiled coil (MCC) examples have focused their efforts on mimicking the active sites of native metalloproteins.

Our overreaching objective was to develop de novo designed CC peptides, to generate miniature protein scaffolds with well-defined secondary, tertiary and quaternary structure, and with which structure-function relationships can more readily be established. Then we have investigated their metal binding (a range of bio & eco relevant transition metals and lanthanides) capability and interrogated their coordination chemistry, and attempted to use the MCC as catalysts, for which a real academic and industrial need exists.
The initial task of our project was to develop de novo designed CC peptides as novel ligands for metal ions to generate a new class of protein-based inorganic complexes. Taking advantage of peptide design principles, O-donor ligands (Asparagine and Aspartate residues) were introduced into a library of parallel three stranded CCs. These were synthesized, purified and characterized. We then explored their binding capability with a range of metals including Sc3+, VO2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+ and Y3+ and lanthanides (La3+, Gd3+ and Tb3+) and interrogated their coordination chemistry. We have attempted to use some of the lanthanide CC as catalysts for phosphate hydrolysis and Aldol reactions. But the yield of the reaction products was lower than that for the control experiments with Ln3+ alone.

Furthermore, we have used 139La NMR as a tool to probe the dynamic nature and coordination chemistry of CCs upon binding with a La3+ ion. The line width of the 139La NMR signal helped us to ascertain the exchange rate of La3+ between the free and protein-bound states, which we believe may be contributing to their poor catalytic performance.

MCCs were also probed by double electron-electron resonance (DEER) spectroscopy, as this can selectively detect the paramagnetic species and ignore the diamagnetic background. In particular, site-directed spin labeling of a protein moiety combined with DEER spectroscopy has emerged as a powerful tool to investigate the structural and the dynamical aspects of biomolecules. In view of the above, we have developed a series of spin-labeled CCs and employed DEER for measuring distances between the spin label and paramagnetic metal centers Cu2+ or Gd3+.

As a result of this work, seven posters in the field of MCC peptides were presented in the following national and the international conference meetings.
ISABC2017: 14th International Symposium on Applied Bioinorganic Chemistry, 7-10 Jun 2017 Toulouse, France. Title: “La3+ binding to a series of de novo designed coiled coils-probed by 139La-NMR”; Postgraduate Symposium on Nanoscience and Nanotechnology, December 13th 2016, Title: “Binding of first row transition metals to a de novo designed coiled coil peptide”; Postdoctoral / Early Researcher, Career Development and Training (PERCAT) Gala Conference, October 27th 2016, Title: “Copper(II) and Zinc(II) selective binding de novo designed coiled coil peptide”; Engineering and Physical Sciences (EPS) Research Conference (internal event), October 25th 2016, University of Birmingham (UOB), Birmingham, UK. Title: “Copper(II) interacting de novo designed coiled coil peptide”; 13th European Biological Inorganic Chemistry Conference (EUROBIC-13), August 29th to September 1st, 2016, Budapest, Hungary. Title: “Binding of first-row transition metals to a de novo designed coiled coil peptide is consistent with the Irving William series”; Marie Skłodowska-Curie Actions Conference ESOF Satellite Event ‘Research and Society’ (MSCA ESOF-2016), July 28th to 29th 2016, The University of Manchester, Manchester, UK. Title: “De novo designed first row transition metal coiled coils”; The Dalton 2016 meeting (DALTON-2016), March 29th to 31st 2016, University of Warwick, Coventry, UK. Title: “De novo designed lanthanide coiled coils as catalysts in phosphodiester hydrolysis reaction in aqueous medium”.
"During this two-year period, the School of Chemistry, UOB has provided a unique environment to enrich my training in design, synthesis and purification of de novo designed CCs and in a diverse range of modern analytical techniques to characterize and study their structure-function relationships. I have successfully prepared a range of transition metal bound CCs and explored their coordination chemistry. We have achieved, insight into the La3+ ion bound isomeric CC peptide series by 139La-NMR spectroscopy. I have been also encouraged to develop a spin-labeled CC series for distance measurement based on DEER spectroscopy. From which we have been able to measure the distance between a paramagnetic metal center and a spin-labeled residue selectively introduced into the CC sequence.

I have also developed a series of oxidovanadium VO2+ coiled coil VCC peptides. These VCC’s are the first and ever reported and these finding may be lead to achieve potential (anti-diabetic) insulin mimetic applications.
I have also been actively involved in the University of Birmingham training programs to advance my professional skills package, which includes POD (People and Organizational Development) Grant writing, Career Development and Teacher Training and Public Engagement sessions for Outreach activities organized by STEM-UK as an ambassador for the West Midland hub. I am also an active member of UOB Marie Curie Association and Marie Curie Alumni (UK Chapter) and participated in several meetings. These scientific, as well as social meets and research collaborations, were offered me to develop long-lasting relationships which are ideal for my career development. The Royal Society has even recommended to the UK-home office to offer me the Exceptional Talent Visa to extend my stay to attain research goals in the UK. Recently, the ""RSC Newton-India Fund Researcher Link Workshops"" selected me for a prestigious, fully funded, research visit to India (IIT-Kanpur) to participate and present my ‘Spin Labelled MCC work’ in the ‘Protein-Metal-Diseases’ workshop.

Due to the topical nature of this research, the work has been well received by the scientific community: Seven contributions to national and the international conferences have been presented, and further journal manuscripts are in preparation.