Multiple Hemoglobins of Catostomid Fish

Multiple hemoglobins from a fish (Catostomus clarkii) were separated and characterized by electrophoresis, column chromatography, ultracentrifugation, end group analysis, and oxygen equilibria studies. The hemoglobins were all tetramers of α and β chains. Two different α chains were detected in unfractionated hemoglobins. Two major β chains were isolated from the hemoglobin components which migrated electrophoretically toward the anode at pH 8.6. Two additional β chains, which were constituents of hemoglobins that migrated toward the cathode, could not be separated from the α chains. The β chains of the anodal and cathodal hemoglobin components of an individual fish were subjected to amino end group analyses with a sequenator. The partial sequences of the βa and βb chains of the anodal components differed by l10%, a finding consistent with the presence of mixed α2βaβb tetramers among the hemoglobins. The NH2-terminal segments of the two β chains of the cathodal hemoglobins were also similar to each other, but differed from the β chains in the anodal components by the same order of magnitude (40 to 45%) as the α and β chains of mammalian hemoglobins. Unlike the anodal components, the cathodal hemoglobins showed no Bohr effect. The chemical groups responsible for most of the Bohr effect were absent in the α and β chains of the cathodal components. These observations were used to propose a possible role for the cathodal hemoglobins in helping to maintain intrastream niche segregation of sympatric catostomid species.