Team:IIT Delhi/Parts

Part:BBa_K1395001-nrfA gene (Nitrite reductase enzyme) under constitutive promoter

• ✔ This part is a combination of constitutive Promoter (BBA_J23119) and nrfA gene (BBA_k1153001). The nrfA gene (Biobrick no. BBA_k1153001) encodes for the Nitrite reductase enzyme (also known as ccNiR, source E.coli K12) which detoxifies nitrogen oxides (NOx) to ammonia (NH3). This gene was obtained from BBA_k1153001 and is 3A assembly (RFC10) compatible. The Constitutive Promoter (BBA_J23119) is the "consensus" promoter sequence and the strongest member of the constitutive promoter family developed by John Christopher Anderson of UC Berkeley.This promoter can be used to tunes the expression level of constitutively expressed parts.The nrfA gene is expressed under this constitutive promoter. Its expression is based on the availability of RNA polymerase holoenzyme and the expression is not affected by any transcription factors.
• ✔ Consequently, nrfA may well act on sulphite ions in the cell. Sulphite reduction by NrfA generates sulphide in a six-electron process that appears to parallel nitrite ammonification although the reaction pathway, and indeed the physiological role of this reaction, are presently unclear. Steady-state parameters describing NrfA sulphite reduction that may inform on the possible in cells. Consequences of interactions between sulphite and NrfA have not been reported to date. However, where rates of sulphite reduction are documented they are at least as high as those of dedicated sulphite reductases although several orders of magnitude less than those for nitrite reduction under comparable conditions. It may also be significant that Sulfite (SO32-) can bind as the distal ligand to the active site heme. This suggests that sulphite will compete with nitrite and nitric oxide for binding to NrfA and, since it is reduced considerably more slowly than those substrates, its presence may have a significant impact on the rates of reduction of the nitrogenous substrates.