Stem-loop structures at the 3' end of tobacco Rubisco large subunit mRNA.

There are two inverted repeat nucleotide (nt) sequences, each capable of forming a stem-loop structure (sls) at the 3' end of the tobacco Rubisco large subunit mRNA (rbcL). The smaller sls is followed by a larger sls. The in vivo functions of the 3' sls of the rbcL mRNA were characterized using the Escherichia coli system. S 1 mapping of the rbcL transcripts synthesized in E. coli revealed that the 3' end of a major transcript in the bacterial cell is almost identical to the 3' end of authentic chloroplast (cp) rbcL mRNA. This native 3' end is located 4 nt downstream from the larger sls for the cp mRNA and 6 nt for the bacterial transcript, respectively. Deletion experiments show that the larger sls is essential for producing the native 3' end of rbcL mRNA in E. coli. The sls do not function as an efficient transcription terminator but can stabilize upstream mRNA segments in vivo.