A maturase that specifically stabilizes and activates its cognate group I intron at high temperatures

摘要

Folding of large structured RNAs into their functional tertiary structures at high temperatures is challenging. Here we show that I-Tnal protein, a small LAGLIDADG homing endonuclease encoded by a group I intron from a hyperthermophilic bacterium, acts as a maturase that is essential for the catalytic activity of this intron at high temperatures and physiological cationic conditions. I-Tnal specifically binds to and induces tertiary packing of the P4-P6 domain of the intron: this RNA protein complex might serve as a thermostable platform for active folding of the entire intron. Interestingly, the binding affinity of I-Tnal to its cognate intron RNA largely increases with temperature; over 30-fold stronger binding at higher temperatures relative to 37 degrees C correlates with a switch from an entropy-driven (37 degrees C) to an enthalpydriven (55-60 degrees C) interaction mode. This binding mode may represent a novel strategy how an RNA binding protein can promote the function of its target RNA specifically at high temperatures. (C) 2010 Elsevier Masson SAS. All rights reserved.