CscB is a cell membrane protein that plays an integral role in transporting sucrose across the membrane as it is a sucrose-proton symporter. It is compatible in many strains of Synechococcus elongatus, including 2973, 6803 and 7942 . S. elongatus is unique in that its cell membrane proton gradient is generated by maintaining a surplus of protons inside the cell . Sucrose can then be exported from the cell using the proton gradient. Our codon-optimized BioBrick is 1248 bp long. We made a point mutation at the 383rd base to eliminate an illegal PstI cut site.
Currently, BBa_E0030 is a commonly used EYFP BioBrick. We codon-optimized the BioBrick for use in photosynthetic cyanobacteria.
PidiA is a ferrous-ion repressible promoter native to cyanobacteria. The source of the PidiA DNA is a close relative to our chassis (S. elongatus PCC 7942). The promoter features a palindromic repeat which is suggested to be activated by the binding of IdiB, its gene immediately downstream of the idiA gene, in a ferrous deficient environment .
PcpcB1A1 features two promoter sequences within the promoter, both of which were included in the BioBrick. For this promoter, derived from S. elongatus PCC 7942, we kept about 100 bp of upstream and downstream regions, the latter of which was cropped immediately before the ATG start codon. Studies have found that Pcpc can also be used in E. coli.
For the BioBrick, we kept most of the original promoter, including a crucial upstream element and the core promoter sequence. Our final BioBrick is 157 bp in length.
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