Auracyanin, a blue copper protein from the green photosynthetic bacterium Chloroflexus aurantiacus

A small, type 1 blue copper protein has been isolated from the green photosynthetic bacterium Chloroflexus aurantiacus . This protein, named auracyanin, appears to be peripherally associated with the cytoplasmic membrane, with a midpoint potential of +240 mV and a moler extinction coefficient of epsilon sub(596) = 2900 M super(-1) cm super(-1). ESR spectra exhibit rhombic distortion and give no indication of interaction between the coppers. The function of auracyanin is not yet known, although its redox properties are compatible with a role in photosynthetic and/or respiratory electron flow.