E. coli trpE polar mutations are 10 times more polar on trpD gene expression than on downstream (trpC, B, or A) gene expression. This effect was shown to be the result of "translational coupling," in which efficient translation of trpD mRNA reqiures efficient translation of the end of trpE mRNA. The trpE-trpD intercistronic punctuation region consists of overlapping stop and start codons, and the trpE and trpD gene products form a functional complex in the cell. In light of these observations and characteristics, several models for the mechanism of translational coupling are considered.
- Received February 26, 1980.