A carotenoprotein from chromatophores of Rhodospirillum rubrum

Abstract

A carotenoprotein has been obtained by SDS-solubilization of Rhodospirillum rubrum chromatophores. It was then purified by (NH 4) 2SO 4 precipitation and Sephadex G-200 filtration. SDS-polyacrylamide gel electrophoresis revealed a single protein with a molecular weight of about 12,000. The absorption spectrum of the complex is entirely different from the usual three peaked carotenoid spectrum, it has only a major peak at 370 nm. However, after acetone extraction the spectrum of spirilloxanthin reappears. The fact that the carotenoid associates with a specific protein provides strong evidence that the complex originates from the chromatophores and is not a preparative artefact.