High-level production of recombinant sulfide-reactive hemoglobin I from Lucina pectinata in Escherichia coli: High yields of fully functional holoprotein synthesis in the BLi5 E. coli strain

Abstract

Hemoglobin I (HbI) from Lucina pectinata is a monomeric protein composed of 143 amino acids with high sulfide affinity. Its unique heme pocket contains three residues not commonly found in vertebrate globins: Phe 29 (B10), Gln 64 (E7), and Phe 68 (E11), which are thought to be important for high affinity for hydrogen sulfide. Recombinant HbI (rHbI) and several site-directed mutants were cloned and expressed in Escherichia coli yielding high amounts of protein. The highest rHbI protein yield was obtained when the HbI cDNA was cloned into the pET28 (a+) expression vector, transformed into BLi5 cells, the induction performed with 1 mM IPTG at 30 °C and TB medium was supplemented with 30 μg/mL hemin chloride and 1% glucose. The highest yield obtained of HbI was 32 mg/L of culture using Fernbach flasks. UV/Visible spectral analysis showed that rHbI binds heme and ESI-MS shows that its molecular weight corresponds to the expected size. Kinetic studies with H 2S confirmed that rHbI and HbI have identical binding properties, where the k ON for the clam’s Hb is 2.73 × 10 4 M −1 s −1 and for rHbI is 2.43 × 10 4 M −1 s −1.