tailieunhanh - Báo cáo khoa học: Structure of RNase Sa2 complexes with mononucleotides – new aspects of catalytic reaction and substrate recognition

Although the mechanism of RNA cleavage by RNases has been studied for many years, there remain aspects that have not yet been fully clarified. We have solved the crystal structures of RNase Sa2 in the apo form and in complexes with mononucleotides. These structures provide more details about the mechanism of RNA cleavage by RNase Sa2. | Structure of RNase Sa2 complexes with mononucleotides -new aspects of catalytic reaction and substrate recognition Vladena Bauerova-Hlinkova1 Radovan Dvorsky2 Dusan Perecko1 Frantisek Povazanec3 and Jozef Sevcik1 1 Institute of Molecular Biology Slovak Academy of Sciences Bratislava Slovakia 2 Max Planck Institute for Molecular Physiology Dortmund Germany 3 Faculty of Chemistry and AgriculturalTechnology STU Bratislava Slovakia Keywords binding subsite complex structure RNA hydrolysis RNase substrate recognition Correspondence V. Bauerová-Hlinková Institute of Molecular Biology Slovak Academy of Sciences Dubravska cesta 21 84551 Bratislava Slovakia Fax 421 2 59307416 Tel 421 2 59307410 E-mail Received 24 June 2008 revised 23 May 2009 accepted 29 May 2009 doi Although the mechanism of RNA cleavage by RNases has been studied for many years there remain aspects that have not yet been fully clarified. We have solved the crystal structures of RNase Sa2 in the apo form and in complexes with mononucleotides. These structures provide more details about the mechanism of RNA cleavage by RNase Sa2. In addition to Glu56 and His86 which are the principal catalytic residues an important role in the first reaction step of RNA cleavage also seems to be played by Arg67 and Arg71 which are located in the phosphate-binding site and form hydrogen bonds with the oxygens of the phosphate group of the mononucleotides. Their positive charge very likely causes polarization of the bonds between the oxygens and the phosphorus atom leading to electron deficiency on the phosphorus atom and facilitating nucleophilic attack by O2 of the ribose on the phosphorus atom leading to cyclophosphate formation. The negatively charged Glu56 is in position to attract the proton from O2 of the ribose. Extended molecular docking of mononucleotides dinucleotides and trinucleotides into the active site of the enzyme allowed us to better understand the