The Effect of Protein Stability on Interactions of Apomyoglobin Forms with Phospholipid Membranes

Abstract

The protein structure can be strongly influenced by phospholipid membranes. As it follows from our papers, apomyoglobin structure undergoes a transition from the native to some intermediate state upon interaction with small negatively charged phospholipid vesicles acting as a moderately denaturing agent. In this work, interaction of apomyoglobin and its mutant forms with artificial membranes is studied by tryptophan fluorescence and CD in the far UV-region. It is shown that a negatively charged phospholipid membrane can structure the unfolded protein into the same intermediate state. The nature of this phenomenon consists in selective stabilization of the intermediate state structure. The rate of interactions between apomyoglobin mutant forms and phospholipid membranes depends mainly on the protein molecule stability, as well as on the charge of the membrane surface and the phospholipid vesicles concentration. This rate increases with decreasing protein stability. The importance of the obtained results for the folding of membrane proteins and the choice of the pathway for target delivery of protein drugs are discussed. This work was supported partly by the Howard Hughes Medical Institute Award 55005607 to A.V. Finkelstein, by the RAS Program “Molecular and Cellular Biology”, by Federal Agency for Science and Innovations 02.740.11.0295, and Program of Scientific Schools 2791.2008.4.