Heat shock inactivates a supernatant factor(s) specifically required for efficient expression of the amp gene in Escherichia coli.

A 160,000 x g supernatant of E. coli extract prepared from cells grown at 30 degrees C stimulated specifically the expression of the amp gene on pBR322 and pBR328 in an in vitro gene expression system from E. coli. This activity of the supernatant was markedly reduced when the cells were exposed to 42 degrees C for 30 min prior to preparing the supernatant. These results are consistent with the view that heat shock-induced repression of the amp gene expression is due to inactivation of a supernatant factor(s) required for effective expression of the amp gene.