[Mitochondrial membrane proteins of lower vertebrates].

Mitochondria from the liver, heart and skeletal muscles of lower vertebrates were studied with the method of IR-spectrometry in the spectral region of amide I and amide II bands. The kinetics of H--D exhange of peptide protons was measured with the same method before and after low-temperature gradual extraction of lipids. It was revealed that mitochondria of different tissues taken from several species of lower vertebrates have a similar stable configuration of amide I band and similar kinetics of H--D exhange in peptide groups of proteins (35--40% of labile peptide protons and 40--50% of stable ones). This suggests that mitochondrial proteins have a similar conformation in membranes. In the first hour of gradual low-temperature extraction of phospholipids from liver mitochondria of the frog (chloroform-methanol, 5 : 1), the increase in labile protons content and the decrease in stable ones could be detected in mitochondrial proteins. During the next 5 hours of extraction, the quantity of labile peptide protons and the content of phospholipids in the extract remained unchanged. Low-temperature extraction of heart mitochondria of the frog Rana temporaria with less polar solutions (chloroform-methanol, 30 : 1 or 20 : 1) gave no rise in the content of labile peptide protons in spite of the large amounts of extracted phospholipids.. These data indicate that tissue specificity of mitochondria is based primarily on the phospholipid component of membranes. The regulatory mechanisms which stabilize the optimal conformation of membrane proteins are different in liver and heart mitochondria.