tailieunhanh - Báo cáo khoa học: Unusual metal specificity and structure of the group I ribozyme fromChlamydomonas reinhardtii23S rRNA

Group I intron ribozymes require cations for folding and catalysis, and the current literature indicates that a number of cations can promote folding, but only Mg 2+ and Mn 2+ support both processes. However, some group I introns are active only with Mg 2+ , . three of the five group I introns in Chlamydomonas reinhardtii. We have investigated one of these ribozymes, an intron from the 23S LSU rRNA gene of Chlamydomonas reinhardtii (), by determining if the inhibition by Mn 2+ involves catalysis, folding, or both | ềFEBS Journal Unusual metal specificity and structure of the group I ribozyme from Chlamydomonas reinhardtii 23S rRNA Tai-Chih Kuo1 Obed W. Odom2 and David L. Herrin2 1 Department of Biochemistry Tapei MedicalUniversity Taiwan 2 Section of Molecular Celland DevelopmentalBiology and Institute for Cellular and Molecular Biology University of Texas Austin TX USA Keywords Fe2 -EDTA group I intron Mn2 RNA structure RNA-metalinteractions Correspondence D. L. Herrin Section of Molecular Celland DevelopmentalBiology 1 University Station A6700 University of Texas at Austin Austin TX 78712 USA Fax 1 512 4713843 Tel 1 512 4713843 E-mail herrin@ Website http MCDB Received 9 February 2006 revised 3 April 2006 accepted 12 April 2006 doi Group I intron ribozymes require cations for folding and catalysis and the current literature indicates that a number of cations can promote folding but only Mg2 and Mn2 support both processes. However some group I introns are active only with Mg2 . three of the five group I introns in Chlamydomonas reinhardtii. We have investigated one of these ribozymes an intron from the 23S LSU rRNA gene of Chlamydomonas reinhardtii by determining if the inhibition by Mn2 involves catalysis folding or both. Kinetic analysis of guanosine-dependent cleavage by a ribozyme that lacks the 3 exon and intron-terminal G shows that Mn2 does not affect guanosine binding or catalysis but instead promotes misfolding of the ribozyme. Surprisingly ribozyme misfolding induced by Mn2 is highly cooperative with a Hill coefficient larger than that of native folding induced by Mg2 . At lower Mn2 concentrations metal inhibition is largely alleviated by the guanosine cosubstrate GMP . The concentration dependence of guanosine cosubstrate-induced folding suggests that it functions by interacting with the G binding site perhaps by displacing an inhibitory Mn2 . Because of these and other

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