DEPENDENCE OF THE GENE-EXPRESSION LEVEL I N ESCHERICHIA-COLI ON THE STRUCTURE OF THE TRANSLATION INITIATION REGION .2. SECONDARY STRUCTURE OF THE TRANSLATION INITIATION REGION

The expression levels of genes that are transcribed to give mRNAs with identical leader sequences and even with identical extended coding re gions may differ considerably. In order to determine the mechanism of this phenomenon, secondary structures of some mRNAs synthesized from a series of expression plasmids were studied. It was shown that the eff ect of the mRNA secondary structure in the translation initiation regi on on the initiation efficiency is due not only to the hairpin formati on in this region but also to long-range interactions. When complement ary structures tighter than those resulted from the interaction of reg ions SD, UB1, UB2, and DB with 16S rRNA are formed, the efficiency of the translation initiation and, consequently, the expression level dec rease.