crystal structure analysis reveals functional flexibility in the selenocysteine-specific trna from mouse晶体结构分析揭示了selenocysteine-specific trna从鼠标功能的灵活性.pdf

Crystal Structure Analysis Reveals Functional Flexibility in the Selenocysteine-Specific tRNA from Mouse Oleg M. Ganichkin, Ekaterina A. Anedchenko, Markus C. Wahl* ¨ Abteilung Strukturbiochemie, Freie Universitat Berlin, Berlin, Germany Abstract Background: Selenocysteine tRNAs (tRNASec) exhibit a number of unique identity elements that are recognized specifically by proteins of the selenocysteine biosynthetic pathways and decoding machineries. Presently, these identity elements and the mechanisms by which they are interpreted by tRNASec-interacting factors are incompletely understood. Methodology/Principal Findings: We applied rational mutagenesis to obtain well diffracting crystals of murine tRNASec. Sec DGCCA Sec ˚ tRNA lacking the single-stranded 39-acceptor end ( RNA ) yielded a crystal structure at 2.0 A resolution. The global structure of DGCCA Sec Sec ˚ RNA resembles the structure of human tRNA determined at 3.1 A resolution. Structural comparisons revealed flexible regions in tRNASec used for induced fit binding to selenophosphate synthetase. Water molecules located in the present structure were involved in the stabilization of two alternative conformations of the anticodon stem-loop. Modeling of a 29-O-methylated ribose at position U34 of the anticodon loop as found in a sub-population of tRNASec in vivo showed how this modification favors an anticodon loop conformation that is functional during decoding on the ribosome. Soaking of crystals in Mn2+-containing buffer revealed eight