Dimer-tetramer transition in hemoglobin from Liophis miliaris—III. The phenomenon in snake species of different evolutionary levels

Abstract

1. 1. The primitive snake Boa constrictor presents in the stripped hemolysate one component which from O2, equilibrium curves produced the following values: log P50 ± −0.1 and Hill coefficient nH = 1.1, independent of pH. 2. 2. Bothrops alternatus, an evolved snake, presents two components in the hemolysate with functional parameters: log P50 = 0.4 and nH = 1.7 at pH 7.1, decreasing to log P50 = −0.1 and nH ± 1.4 at pH 8.2. 3. 3. In the presence of ATP, an increase to log P50 ± 0.9 and nH ± 2 is found in both snake hemolysates, up to pH 7.8 4. 4. Molecular weight determinations by gel filtration at pH 8 show only the dimeric form (mol. wt 32,000) in B. constrictor hemolysate, and dimers and tetramers (mol. wt 64,500) in that of B. alternatus. 5. 5. The Hill plots as a function of O2 tension show for B. alternatus hemolysate a shift from deoxytetramer nH = 2.02 to oxydimer nH = 0.88 as occurs in L. miliaris. For B. constrictor hemoglobin the nH remains 1.0 independent of the O(in2) tension.