THE SEDIMENTATION CONSTANTS OF THE RESPIRATORY PROTEINS

Abstract

A systematic study of the sedimentation constants of the respiratory blood proteins throughout the animal kingdom has been carried out. A small quantity of the soln. enclosed in a sector-shaped cell is exposed to a strong centrifugal field in the ultracentrifuge and the movement of the boundary between the solvent and the dissolved protein molecules determined by taking photographs during centrifuging. The main results may be summarized as follows. Respiratory proteins contained in blood corpuscles have always low sedimentation constants. Hemoglobin characterized by the sedimentation constant 4.4 X 10-13 occurs only in the higher vertebrates. The blood corpuscles of the lowest vertebrates (Cyclostomata) as well as of the capitellide worms have a respiratory protein of much lower sedimentation constant, 2.1 X 10-13; glyceride worms and lamellibranchs 3.5 X 10-13; holothurians, 26 X 10-13. Respiratory proteins dissolved in the blood plasma have as a rule high sedimentation constants and high molecular weights. The only exception is the blood pigment of Chironomus larvae, which has a sedimentation constant almost identical with that of the Cyclostomata and the capitellide worms. All the polychaete worms and hirudineans with the respiratory protein dissolved in the blood have the constant 57.5 X 10-13. Some of these proteins are red (erythrocruorin) others are green (chlorocruorin) . The oligochaete worms have a constant 61.9 X 10-13, very close to that of the other worms. Some of the crustacean families show the sedimentation constant 16.9 X 10-13 (hemocyanin and erythrocruorin), others 23.5 X 10-13, and one of them 340 X 10-13. In the blood of the xiphosureans and scorpions a hemocyanin of the latter constant occurs. All the gastropods except Planorbis with the constant 34.0 X 10-13 have 100.1 X 10-13. It is obvious from these regularities that biological kinship is often accompanied by identity of the sedimentation constant.