Intracellular protein catabolism. IX. Hydrophobicity of substrate proteins is a molecular basis of selectivity.

Double-labeled cytosol proteins from rat liver (3H in short-lived, 14C in long-lived proteins) were fractionated by using siliconized glass-beads, phenylsepharose and octylsepharose. Always the short-lived proteins are more tightly bound to the hydrophobic matrix. The same distribution was found with monkey liver substrate proteins. Therefore it is concluded that the different degrees of exposure of superficial hydrophobic areas on substrate protein molecules are a molecular basis of selectivity of the intracellular protein catabolism.