Isolation and Characterization of Chloroform-Soluble Proteins from Rat-Liver Mitochondria and Other Fractions.

Chloroform-soluble proteins have been isolated free from phosphatides from rat liver mitochondria, microsomes and cytosol by chromatography on Sephadex LH-20 columns. The amino acid composition of the chloroform-soluble and insoluble proteins has been estimated. The chloroform-soluble proteins from mitochondria and cytosol have a higher content of hydrophobic and a lower content of acidic amino acids compared to the corresponding chloroform-insoluble proteins. No marked differences were found between chloroform-soluble and insoluble proteins from microsomes. In contrast to the acidic chloroform-insoluble proteins, all chloroform-soluble proteins are basic. From the amino acid composition the amount of chloroform-soluble proteins has been estimated. Mitochondrial membranes contain 1.6%, mitochondrial matrix proteins less than 0.025%, microsomes 3.0% and the cytosol 0.15% from total proteins. The molecular weight distribution of chloroform-soluble proteins synthesized in mitochondria has been measured by gelelectrophoresis. The molecular weights range from about 7000 to 30000. The turnover of chloroform-soluble proteins from mitochondria and cytosol is higher than from the corresponding chloroform-insoluble proteins. A part of mitochondrial chloroform-soluble proteins (about 30%) is synthesized within the mitochondria. [ABSTRACT FROM AUTHOR]