A Comparative Study of the Oxygen Transport Proteins of Dendrostomum pyroides

Abstract

Abstract Hemerythrins have been isolated from muscle, the vascular system, and the coelom of the sipunculid Dendrostomum pyroides. Muscle hemerythrin (myohemerythrin), vascular hemerythrin, and coelomic hemerythrin have been purified by ammonium sulfate precipitation and have been partially characterized. The ultraviolet and visible absorption and circular dichroic spectra of myohemerythrin and vascular hemerythrin closely resemble those of the coelomic protein, indicating that these hemerythrins have similar iron sites. Far-ultraviolet circular dichroism measurements reveal that the three hemerythrins also have similar secondary structures. In contrast, amino acid analysis shows that the three proteins differ substantially in primary structure. Vascular hemerythrin and coelomic hemerythrin each occur as oligomeric (probably octameric) molecules while myohemerythrin occurs only as a monomer.