The Molecular Ecology ofFundulus heteroclitusHemoglobin-Oxygen Affinity

Abstract

Animals faced with environmental perturbations must adapt or face extinction. The respiratory complex, specifically hemoglobins, is perhaps the best system to study such adaptation because it exists at the organism—environment interface. Fish are particularly useful models because they respond directly to such environmental variables as temperature, oxygen, pH, carbon dioxide, and salinity. Our experiments have addressed the molecular, cellular, and physiological mechanisms employed by fish to maintain respiratory homeostasis in the wake of changing temperature and oxygen. Immediate, intermediate, and long-term adaptation can only be understood when the hemoglobin's ligand binding properties and the cellular and hormonal regulation of various ligands are considered simultaneously. We describe a detailed thermodynamic model for the binding of oxygen, protons, and organic phosphates to hemoglobin; discuss the role of multiple hemoglobins; and present evidence for physiological and genetic regulation of hemoglobin's major allosteric modifiers in response to environmental stress in the mummichog, Fundulus heteroclitus