Structure Formation Mechanism of Helix-Type Membrane Protein

点击翻译按钮获取中文摘要

Three kinds of denaturation experiments were performed for a typical membrane protein, bacteriorhodopsin, in order to estimate the contribution of various factors to the structure formation of membrane proteins. The results were as follow : 1. Bacteriorhodopsin denatured by the addition of alcohols. In the alcohol denaturation, the tertiary structure was destroyed with the secondary structure remained intact. 2. Bacteriorhodopsin did not denature in pure hexane. However, the structure was destroyed by the addition of small amount of alcohol, indicating that the hydroxyl group is responsible for the alcohol denaturation of membrane proteins. 3. The activation energy of the thermal denaturation was estimated from the temperature dependence of the denaturation kinetic constant. The activation energy of about 40 kcal/mol corresponds to about ten hydrogen bonds in membrane. Tihs number is the half of possible hydrogen bonds between transmembrane helices. Consequently, the mechanism of the structural stability is due to the polar interactions such as hydrogen bonds and ion pairs between transmembrane helices.