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Summary
Novelty: A pH regulated promoter is disclosed which is said to have been used to express several different therapeutic proteins in E. coli. This may provide a cheap way of inducing expression, in a large scale fermenter, of proteins such as bovine somatotropin, interleukin-1β, CD-4 and porcine somatotropin.
Biology: A 3714 base pair DNA sequence was detected in E. coli which appears to give a large increase of expression when the external pH is reduced from a pH of 7.5 to 5.5. The sequence was found by using a promoterless β-galactosidase gene and DNA from the cadA gene region. A vector was constructed which contained a 3.7 kb portion of this region and a BamHI. site downstream for the insertion of a desired gene. The expression of β-galactosidase was said to increase from 329 units to 13,918 units. The pH of the bacterial culture was shifted by introducing MES buffer (pH = 4.0) until the pH of the culture reached 5.8.