Jindrich Hasek

Dynamic theory of protein crystallization

Diffraction quality of protein crystals depends on periodicity of its molecular skeleton. Inspection of PDB shows that only 20 % of crystal mass is enough to form a rigid skeleton of protein molecules responsible for diffraction. Protein crystals remind high-tech modern buildings relying on the framed skeleton strong in tension and compression. Therefore, the development of tools enforcing protein molecules to adhere each other in the required unique way is important.

4-acetamido-3,3,5,5-[2H4]-2,2,6,6-tetra([2H3]methyl)piperidin-1-yloxyl 0.33-hydrate.

The asymmetric unit of the title compound, C11H5D16N2O(2).0.33H2O, is formed by three crystallographically independent piperidin-1-yloxyl molecules and a molecule of water. The molecules are crosslinked by nine hydrogen bonds into layers parallel with the ac plane. The water molecule contributes to the stability of the low-symmetry arrangement by four hydrogen bonds.

Cage-like hexamers of cold-active β-galactosidase from Arthrobacter sp. C2-2

β-galactosidase catalyzes hydrolysis of galactosyl moiety from non-reducing termini of oligosaccharides or from glycosides. Crystals of β-galactosidase from psychrotrophic bacterium Arthrobacter sp. C2-2 were grown by vapor diffusion technique and X-ray diffraction data were collected up to 1.9 A [1]. Molecular replacement solution in P21 space group revealed six molecules arranged in cage-like hexameric structure with cca 60,000 non-hydrogen atoms per asymmetric unit. The compact hexamers are characterized by three types of channels, six active sites open towards the central cavity, high number of buried water molecules within the protein and Na and Mg ions bound in vicinity of the active site. Comparison to E.coli βgalactosidase shows both similarities and significant differences regarding the active site and oligomerization mechanism. Acknowledgement: This work was supported by GACR (project 204/02/0843/A) and by the Grant Agency of the Academy of Sciences of the Czech Republic (project KJB500500512).