Interaction of a 3' RNA region of the mustard trnK gene with chloroplast proteins.

The 3' flanking region of the chloroplast trnK gene for tRNALys of mustard contains a palindromic sequence previously implicated with transcription termination and/or processing of the precursor RNA. Here we have investigated whether RNA sequences from the trnK 3' region are capable of interacting with chloroplast proteins in vitro. We find specific binding to an RNA region which is located further downstream from the palindromic sequence. The approximate length and position of this 3' binding region is reflected by a 41 nt spanning RNA segment which is protected against RNase T1 digestion by chloroplast protein(s). Competition experiments and sequence analyses suggest that U residues play an essential role in the RNA-protein interaction. Only a small number of proteins, possibly one single species, is in contact with the trnK 3' RNA.