Molecular Assembly of Protein with Liquid-Liquid Phase Separation : Structure, Mechanism, and Function of Elastic Fiber Protein Aggregates

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The essential and key step for the biosynthesis of elastic fiber protein is a self-assembly process of tropoelastin, biogenic precursor protein of elastin. Multiple functions of elastin as an extracellular matrix are derived from the molecular structures established during these 'molecular aggregation process. These important biological processes in the extracellular space are equivalent to the temperature-dependent coacervation of soluble elastin-related peptides. In the present research project, structure, mechanism, and function of elastin coacervate composed of a-elastin or synthetic model polypeptide were investigated.(1)Examination of the liquid-liquid phase separation of elastin water system.Turbidity measurements were employed to survey primarily the characteristics of temperature-dependent coacervation of elastin peptides. Static and dynamic light scattering experiments were also carried out to further investigate the early stage of molecular assembly process. It was shown that the elastin coacervate formation process was affected specifically by metal cations.(2)Elastin coacervate as a protein liquid membrane.Macrocoacervate layer of elastin peptides was stable enough to utilize as a liquid ion-exchange membrane. Selective and specific transport processes for Ca^<2+> ions were observed. It was also demonstrated that the present system is useful to investigate the interactions between protein and metal cations.(3)Structure, mechanism, and function of elastin coacervate.Selective interactions of Ca^<2+> ions with pentapeptide, Val-Pro-Gly-Val-Gly, backbone were observed in a variety of measurements including CD and NMR sppectroscopy. It was suggested that the fundamental molecular structure responsible to generate elastomeric function of elastin is inevitably subjected to selective interaction of Ca^<2+>.