Enzyme action at RNA-protein interface in DTD-like fold.

The contemporary `RNA-protein world' is exemplified by close associations between many RNAs and proteins which are necessary to carry out important biological processes. DTD-like fold, which is involved in translational proofreading, represents such RNA-protein complexes (RNPCs). Interestingly, it interacts with the substrates in the active site mostly through the main chain, and side chains are dispensable for both substrate specificity and catalysis. It functions at the RNA-protein interface to perform RNA-based catalysis using the 2'-OH of adenosine-76 of tRNA. Such catalytic RNPCs as the DTD-like fold also indicate the probable evolutionary trajectory for the transition from RNA-mediated catalysis to protein-based catalysis.