Small Ribonuclease Mimics

Abstract

Recent progress in investigation of the structures and mechanisms of the function of natural enzymes capable of hydrolyzing p-o bonds in ribonucleic acid is reflected in a number of reviews (Strater et al. 1996; Wilcox 1996; Cowan 1998; Kovall and Matthews 1999). In enzymes, interactions between functional groups of amino acid side radicals result in complex tertiary and quaternary structures that determine the composition of different functional domains of these structural catalysts. The set of amino acids directly involved in catalysis is highly conservative. The amino acids most frequently found in the enzyme active centers are histidine, lysine, arginine, aspartic acid, and glutamic acid residues, their amides, and hydroxyl-containing amino acids. The side chains of these amino acids also form several uniform metallocomplexes with metal ions (Sträter et al. 1996; Hegg and Burstyn 1998; Kozlowski et al. 1999; Kimura 2000). For nucleic acids cleaving enzymes it is suggested that hydrolysis of p-o bonds passes via acid-base catalysis (delCardayre and Raines 1995). In contrast to hydrolysis of c-o bonds, the p-o bonds are very rarely cleaved via nucleophilic catalysis (Gottlin et al. 1998; Iwasaki et al. 1999).