Sulfide-Binding by an Extracellular Hemoglobin

Abstract

The blood of the deep-sea, hydrothermal vent tube worm Riftia pachyptila contains a large, extracellular hemoglobin (Hb) that binds sulfide with a high affinity and capacity both in vitro and in vivo (Arp and Childress, 1981; Arp and Childress, 1983). The animal appears to utilize this binding ability to transport sulfide to internal bacterial symbionts that use it as an energy source. My recent work indicates that this sulfide-binding protein is the Hb molecule itself and that sulfide-binding is a nonheme phenomenon that may occur at disulfide bridges that are the forces holding the submultiples of the giant molecule together. Sulfide-binding capacity may be dependent on the assembly state of this molecule, and assembly state appears to differ between the two Hb-containing fluids in this animal.