To identify some of the determinants in the 19-kilodalton protein of signal recognition particle (SRP19) for binding to signal recognition particle RNA, two mutant derivatives of the SRP19 were constructed, lacking 14 and 24 C-terminal amino acids. Polypeptides were transcribed and translated in vitro and tested for their ability to bind to signal recognition particle RNA by retention of protein–RNA complexes on DEAE–Sepharose. Both mutant polypeptides form complexes with the RNA, demonstrating that the 24 C-terminal amino acids, which include a lysine-rich sequence at positions 136–144, are dispensable. A third mutant polypeptide, in which eight additional amino acids were removed by oligonucleotide-directed digestion of the mRNA, was unable to bind. The amino acids in the sequence PKLKTRTQ correspond to positions 113–120; they are suggested to be involved in interaction with signal recognition particle RNA.Key words: signal recognition particle, site-directed mutagenesis, protein–RNA binding.
Determinants of a protein-induced RNA switch in the large domain of signal recognition particle identified by systematic-site directed mutagenesis