Preliminary Studies On The Relation Between The MRNA Secondary Structure And The Expression Level Of AguA From Thermotoga Maritima

The gene expression in E. coli is correlated with the gene sequence, such as synonymous codon usage preference, the secondary structure of mRNA and signal peptide. The gene aguA ( gene of α-Glucuronidase) from Thermotoga maritima was analyzed by using DNA analysis programs. Some factors were found to affect the expression of aguA in E. coli. Optimization of rare codons and the secondary structure of mRNA was+ made by site directed mutagenesis and directed-convert. The gene and mutants were inserted into the expression vector pTrc-99A and pHsh, transformed into E. coli strain JM109, and gene expression levels were determined. The expression level of mutational gene aguA1 in vector pTrc99A is 0.37×10-2U/mL·OD600 while that of gene aguA is 0.98×10-2 U/mL·OD600, but in vector pHsh they are 0.16 and 0.25 U/mL·OD600, respectively. Then we can reach the conclution that the expression level is positively correlated with the secondary structure of mRNA of TIR.From the expression level of other mutational genes aguA, aguA3, aguA4, aguA5, aguA34, aguA345, we can draw the conclusion that the secondary structure of TIR and the gene sequence effect the expression level, respectively. And the expression level will be affected largely while only several base were replaced, whereas the deep investigation should be needed to elucidate for the biological mechanism.