RNA–protein complexes

Abstract

RNA-binding proteins are an extremely diverse group of proteins, reflecting the diverse functional requirements of cellular RNAs. Whereas the number of structures of RNA-binding proteins or modules is increasing at a reasonable rate, that of protein–RNA complexes increments by only a few each year. The recently determined structure of a complex from the U2 small nuclear ribonucleoprotein particle shows the subtleties of RNA stem–loop recognition by ribonucleoprotein modules. A second structure provides the first direct information on double-stranded RNA recognition by the double-stranded RNA-binding module that occurs in a variety of functionally distinct proteins. Another two new complexes concern proteins interacting with tRNA. The first is methionyl-tRNAfMet transformylase, which has to compete with elongation factor Tu for charged initiator tRNAMet and does so by recognising specific features of the acceptor stem of tRNAfMet. The second is prolyl-tRNA synthetase, complexed with its cognate tRNA, that has to specifically recognise the two guanines common to all tRNA anticodons specific for proline.