Computational Study of Molecular Mechanism for the Involvement of Human Serum Albumin in the Renin-Angiotensin-Aldosterone System.

Human serum albumin (HSA) is an endogenous inhibitor of angiotensin I-converting enzyme (ACE) and, thus, plays a key role in the renin-angiotensin-aldosterone system (RAAS). However, little is known about the mechanism of interaction between these proteins, and the structure of the HSA-ACE complex has not yet been obtained experimentally. The purpose of the presented work is to apply computer modeling methods to study the interaction of HSA with ACE in order to obtain preliminary details about the mechanism of their interaction. Ten possible HSA-ACE complexes were obtained by the procedure of macromolecular docking. Based on the number of steric and polar contacts between the proteins, three leading complexes were selected, the stabilities of which were then tested by molecular dynamics (MD) simulation. Based on the results of MD simulation, the two most probable conformations of the HSA-ACE complex were selected. The analysis of these conformations revealed that the processes of oxidation of the thiol group of Cys34 of HSA and the binding of albumin to ACE can reciprocally affect each other. Known point mutations in the albumin molecules Glu82Lys, Arg114Gly, Glu505Lys, Glu565Lys and Lys573Glu can also affect the interaction with ACE. According to the result of MD simulation, the known ACE mutations, albeit associated with various diseases, do not affect the HSA-ACE interaction. A comparative analysis was performed of the resulting HSA-ACE complexes with those obtained by AlphaFold 3 as well as with the crystal structure of the HSA and the neonatal Fc receptor (FcRn) complex. It was found that domains DI and DIII of albumin are involved in binding both ACE and FcRn. The obtained results of molecular modeling outline the direction for further study of the mechanisms of HSA-ACE interaction in vitro. Information about these mechanisms will help in the design and improvement of pharmacotherapy aimed at modulation of the physiological activity of ACE.