Promoter selection by a bacterial enhancer-like activator element (BELE) in Escherichia coli

The Escherichia coli glnA gene promoter glnAp2 is activated by an element able to act bidirectionally and at variable distance over the DNA. We demonstrate here that this activating element does not influence another promoter, 82p, adjacent to it, from which a gene is transcribed in opposite direction to glnA. Thus, although it displays a great flexibility, this element can activate selectively. The unresponsive promoter and glnAp2 are recognized by RNA polymerases complexed to two different sigma factors. Therefore, we argue that promoter selection by this element is dependent upon distinguishing the proper sigma factor.     

Efficient use of lactose for the lac promotercontrolled overexpression of the main antigenic protein of the foot and mouth disease virus in Escherichia coli under fed-batch fermentation conditions

Abstract: Derivatives of the lac promoter (tac, pac, rac) belong to the strongest bacterial promoters which are frequently used for the induced overexpression of foreign genes in Escherichia coli . However, their use in fermentation processes is strongly restricted because of the high cost of the inducer iso-propyl-β-D-thiogalactopyranoside (IPTG). The aim of this work was to investigate the possibility of using lac-derived promoters in high cell density processes resulting in a high yield of the induced recombinant protein if glucose is the main carbon and energy source. Lactose is tested as inducer of the main antigenic coat protein (VP1) of the foot and mouth disease (FMD) virus in a T7-RNA polymerase expression system. It was shown that lactose is able to induce the expression of the recombinant gene to an amount of the VP1 protein corresponding to 20% of the total cell protein.