Part:BBa_K754000

S. elongatus PCC7942 psbAI promoter

Our part is the Synechococcus elongatus promoter for gene psbAI. This promoter works on a constitutive way, althought its activity can be enhanced or decreased in the presence or absence of light (in nature it works regulated in a circadian cicle). This part is suitable for building light-induced devices.

Usage and Biology

The psbAI gene of the cyanobacterium Synechococcus elongatus PCC 7942 is one of three psbA genes that encode a critical photosystem II reaction center protein, D1. Regulation of the gene family in response to changes in the light environment is complex, occurs at transcriptional and posttranscriptional levels, and results in an interchange of two different forms of D1 in the membrane. Expression of psbAI is downregulated under high-intensity light (high light) in contrast to induction of the other two family members.

Functional Parameters

One of the most crucial determinants of gene expression in cyanobacteria is the initiation of transcription, where several sigma factors are involved in promoter recognition (Mulo et al. 2009). The psbAI promoter has characteristic -35 spaced elements from the E. coli σ70 promoter, but has an atypical -10bp element TCTCCT (Golden et al. 1986) (figure 3), which entails that this promoter doesn't work in E. coli (Schaefer and Golden, 1989) making it difficult to characterize it properly. The smallest psbAI functional promoter region comprises nucleotides -54 to +1, and one or more proteins bind specifically to the psbAI upstream region stimulating, rather than inactivating the transcription (+1 to + 43) (Nair et al. 2001), unlike typical σ70 promoters. A segment of approximately 20bp of the consensus -35 element has been shown to be implicated in both, promoter activation per se and light-responsive expression, this region is characterized by being AT-rich (Nair et al. 2001).