THE SOLUTION STRUCTURE OF THE S1 RNA-BINDING DOMAIN - A MEMBER OF AN ANCIENT NUCLEIC ACID-BINDING FOLD

The S1 domain, originally identified in ribosomal protein S1, is found in a large number of RNA-associated proteins. The structure of the S1 RNA-binding domain from the E. coli polynucleotide phosphorylase has been determined using NMR methods and consists of a five-stranded anti parallel beta barrel. Conserved residues on one face of the barrel and adjacent loops form the putative RNA-binding site. The structure of t he S1 domain is very similar to that of cold shock protein, suggesting that they are both derived from an ancient nucleic acid-binding prote in. Enhanced sequence searches reveal hitherto unidentified S1 domains in RNase E, RNase II, NusA, EMB-5, and other proteins.