In vitro selection of nucleoprotein enzymes

Natural nucleic acids frequently rely on proteins for stabilization or cata lytic activity. In contrast, nucleic acids selected in vitro can catalyze a wide range of reactions even in the absence of proteins. To augment select ed nucleic acids with protein functionalities, we have developed a techniqu e for the selection of protein-dependent ribozyme ligases. After randomizin g a previously selected ribozyme ligase, L1, we selected variants that requ ired one of two protein cofactors, a tyrosyl transfer RNA (tRNA) synthetase (Cyt18) or hen egg white lysozyme. The resulting nucleoprotein enzymes wer e activated several thousand fold by their cognate protein effecters, and c ould specifically recognize the structures of the native proteins. Protein- dependent ribozymes can potentially be adapted to novel assays for detectin g target proteins. and the selection method's generality may allow the high -through identification of ribozymes capable of recognizing a sizable fract ion of a proteome.