HETEROGENEITY AND SUBUNIT COMPOSITION OF THE HEMOGLOBINS OF 5 TILAPIINE SPECIES (TELEOSTEI, CICHLIDAE) OF THE GENERA OREOCHROMIS AND SAROTHERODON

Haemoglobins of five tilapiine species of the genera Oreochromis and S arotherodon were investigated. By gel filtration chromatography a mole cular weight of 67-69 kDa was determined for the tetrameric molecules which remained stable between pH 5.0 and pH 9.1. When subjected to sod ium dodecyl sulphate-Urea-polyacrylamide gel electrophoresis (PAGE), h aemoglobins of all species each were split into monomers of three diff erent molecular weights ranging between 16.3 kDA and 17.6 kDa. Subsequ ently, isoelectric focusing separated haemolysates into about 23 diffe rently charged tetrameric haemoglobins that were arranged in species-s pecific patterns. This diversity was shown to result from the occurren ce of different types of globin chains. By acidic urea PAGE a total of seven major alpha-globins and five major beta-globins were detected a nd species-characteristic chain variants were identified. To determine the globin chain composition of particular haemoglobin tetramers, 26 bands were isolated by isoelectric focusing and analysed by acidic ure a PAGE. Tetramers consisted of doublets of identical alpha- and identi cal beta-chains (alpha(2) beta(2), symmetric tetramers), or combinatio ns of three (alpha(2) beta beta; alpha alpha*beta(2)) or four (alpha alphabeta beta*) distinct chains (asymmetric tetramers). Finally, glo bin chains of Oreochromis niloticus were subjected to partial N-termin al amino acid sequencing. Differences in the composition of the three major beta-chains could be shown, whereas the alpha-chains were N-term inally blocked.