Heterologous expression and purification of the bicarbonate transporter BicA from Synechocystis sp. PCC 6803

The high-flux/low-affinity cyanobacterial bicarbonate transporter BicA is a member of sulfate permease/solute carrier 26 (SulP/SLC26) family and plays a major role in cyanobacterial inorganic carbon uptake. In order to study this important membrane protein, robust platforms for over-expression and protocols for purification are required. In this work we have optimized the expression and purification of BicA from strain Synechocystis sp. PCC 6803 (BicA₆₈₀₃) in Escherichia coli. It was determined that expression with C43 (DE3) Rosetta2 at 37 °C produced the highest levels of over-expressed BicA₆₈₀₃ relative to other strains screened, and membrane solubilization with n-dodecyl-β-D-maltopyranoside facilitated the purification of high levels of stable and homogenous BicA₆₈₀₃. Using these expression and purification strategies, the final yields of purified BicA were 6.5 ± 1.0 mg per liter of culture.