Cooperative homodimeric hemoglobin from Scapharca inaequivalvis. cDNA cloning and expression of the fully functional protein in E. coli.

The overexpression of the fully functional, cooperative homodimeric hemoglobin of the bivalve mollusc, Scapharca inaequivalvis, has been accomplished in E. coli from its cDNA. The latter was isolated by PCR amplification of total RNA and sequenced. The cDNA-derived sequence differed by a single amino acid when compared to that previously obtained from purified protein. Interest in this hemoglobin resides in the unique assemblage of the two identical subunits, with the heme groups facing each other in the inside of the molecule, opposite to that occurring in vertebrate hemoglobins. The results presented here are the basis for future studies of structure/function relationships by site directed mutagenesis.