Difference between revisions of "Part:BBa K239005"

Latest revision as of 18:44, 24 October 2009

NarK promoter, Fnr activated under anaerobic conditions

Sequence contains 2 Fnr, 1 Fis, 4 NarL and 1 IHF binding sites and initiates transcription by RNAP sigma-70. Function: Switched on during anaerobic conditions (low oxygen level -> PoPS output).

Area of application: Detection of when E.coli switches to anaerobic metabolism, or for oxygen dependent induction systems.

Experiments by Kolesnikow et al. (1992) have showed that NarK expression is upregulated 100-fold under anaerobic condtitions and a further 8-fold in the presence of nitrate.

The optimal Fnr binding sequence is TTGAT-4N-ATCAA. (Spiro and Guest, 1990) For the NarK promoter (BBa_K239005) the promoter-proximal Fnr site has a binding region identical to the consensus sequence. The promoter-distal Fnr binding site differs slightly from the optimal binding region. The promoter-distal site is: ATGAT-AAAT-ATCAA. For the modified NarK promoter (BBa_K239006) this sequence has been re-written to the optimal sequence.

Usage and Biology

Fnr is always present in the cell in largely constant amounts. (Spiro and Guest, 1987) In vivo, during anaerobic conditions Fnr becomes activated reversibly. (Engel et al. 1991) During aerobic growth O2 inactivates Fnr by destroying its [4Fe-4S] cluster, which is essential for DNA binding. (Green et al. 1996)

Sequence and Features