A STRUCTURAL AND FUNCTIONAL POLYMORPHISM IN THE HEMOGLOBIN O2 TRANSPORT-SYSTEM OF THE BLOOD CLAM NOETIA-PONDEROSA

A sample of arcid blood clams (Noetia ponderosa) from the Atlantic coa st of Virginia had red blood cells containing a hemoglobin composed of only one electrophoretically separable component. Both the red blood cells and hemoglobin extracts had a moderately high oxygen affinity. A sample from the Gulf of Mexico had red blood cells containing hemoglo bins composed of two components. According to previous reports, this p opulation contains a homodimer of one chain and a heterodimer of that chain plus another. Both the red blood cells and the hemoglobin extrac ts had a much lower oxygen affinity. Thus, in this species, the O2 car rier is qualitatively (and, according to the previous report, quantita tively) polymorphic, and the polymorphism is reflected in respiratory properties as well as quaternary structure. The origin of the differen t hemoglobin phenotypes, however, is not yet clear. (C) 1993 Wiley-Lis s, Inc.