Comparative structural and functional studies of avian and mammalian hemoglobins

Thermal stabilities of chicken, grey lag goose (Anser anser), turkey as avian hemoglobins (Hbs); and human, bovine, sheep and horse as mammalian Hbs in hemolysate form were investigated and compared with oxygen affinities taken from literature. The thermal stability was obtained from thermal profiles using temperature scanning spectrophotometry. The buffer conditions were 50 mM Tris, pH 7.2, and 1 mM EDTA. The average of the inverse temperature transitions, average hydrophobicity, total van der Waals volume, partial molal volume and hydration potential were calculated by computational methods. The hemolysed avian Hbs have a lower oxygen affinity, higher thermal stability and higher self association than the mammalian Hbs. These observations are based on amino-acid composition, influence of ionic effectors, and the presence of Hb D in several avian Hbs. The results indicate that the avian Hbs have a more tense (T) conformation than the mammalian Hbs.