The primary interest of my laboratory is the understanding of the function of proteins by determination and analysis of the crystal structures of these macromolecules at high resolution . In particular, our main focus is the elucidation of the catalytic mechanisms of enzymes. In order to achieve this we try to co-crystallize the enzyme under study in different chemical states along its reaction coordinate and analyze the structures of the Michaelis complex(-es) and other possible intermediates. Moreover, in combination with X-ray crystallography, we employ biochemical methods, e.g. site directed mutagenesis targeting to analysis of the role of selected amino-acid residues in the active sites of enzymes. Another area of interest is the development of rational crystallization methods for proteins and their complexes with partner molecules with the usage of ionic strength reducing agents, e.g. polyethylene glycols (PEGs). We extensively employ synchrotron radiation for our macromolecular crystallography experiments, particularly the energy tunability of the latter that allows the application of anomalous diffraction methods for phasing of the Bragg reflections. Finally, we are interested in the biotechnological applications of the structural analyses, e.g. design and production of more stable and faster biocatalysts in selected ranges of pH and temperature.

Selected Publications

R. Gessmann, C. Kyvelidou, M. Papadovasilaki and K. Petratos (2011) The crystal structure of cobalt-substituted pseudoazurin from Alcaligenes faecalis. Biopolymers 95: 202-207.

R. Gessmann, H. Bruckner and K. Petratos (2003) Three Complete Turns of a 3(10)-Helix at Atomic Resolution: The Crystal Structure of Z-(Aib)11-O t Bu. J. Pept. Sci. 9: 753-762.

Y. Papanikolau, G. Prag, G. Tavlas, C. E. Vorgias, A. B. Oppenheim and K. Petratos (2001) High Resolution Structural Analyses of Mutant Chitinase A Complexes with Substrates Provide New Insight into the Mechanism of Catalysis. Biochemistry 40: 11338-11343.

F. K. Winkler, D. W. Banner, Ch. Oefner, D. Tsernoglou, R. S. Brown, S. P. Heathman, R. K. Bryan, P. D. Martin, K. Petratos and K. S. Wilson (1993) The crystal structure of Eco RV endonuclease and of its complexes with cognate and non-cognate DNA fragments. EMBO J. 12: 1781-1795.

K. Petratos, Z. Dauter and K. S. Wilson (1988) Refinement of the Structure of Pseudoazurin from Alcaligenes faecalis S-6 at 1.55 A Resolution. Acta Crystallogr. B 44: 628-636.