Bohr effect, electron spin resonance spectroscopy and subunit dissociation of the hemoglobin components from the...

Isoelectric points of the two haemoglobin components from the fresh-water turtle, Phrynops hilarii, were estimated by isoelectric focusing electrophoresis (IEF) to be 7.6 and 6.3, respectively for component I (CI) and component II (CII). For further studies, CI and CII were isolated by ion exchange chromatography. At pH 7.1, the estimated intraerythrocytic pH, at 25 degrees C, the values of P50, for the stripped haemoglobins, are: 19 torr for CI; 40 torr for CII and 28 torr for the whole haemolysate (pht). Oxygen binding with the stripped isolated components (CI and CII) and with the whole haemolysate (pht) show that delta log P50/delta pH, in the pH interval from 6.8 to 8.5, to be: CI = -0.35; CII = -0.80 and pht = -0.47. The Bohr curves for CI and CII intercept at pH 7.8. eta 50 for CI was 3 and invariant with pH. CII, at the more acid pH range showed biphasic Hill plots. pht shows a eta 50 that varies with pH. CI is affected by ATP, ADP, GTP and slightly by CO2, whereas CII is totally insensitive to CO2 and ATP. Additionally both components are not affected by inositol phosphates. Electron spin resonance (ESR) spectra of both components at pH 8.4 and 6.4 show that CI fails to undergo a R----T transition, while CII, with the higher Bohr effect, undergoes the R----T transition driven by pH. Molecular sieving studies of the liquid nitrogen stored CI, CII and pht show them to be disulphide polymers, CI with an apparent mol. wt of 150 X 10(3) and CII and pht of 100 X 10(3).(ABSTRACT TRUNCATED AT 250 WORDS)