TITLE:
Calmodulin Bound Aquaporin-0 Reveals Two Distinct Energy Profiles
AUTHORS:
L. K. Balcziak, T. H. Bach, L. R. Montgomery, M. E. Warwick, U. Akgun
KEYWORDS:
Aquaporin-0, Calmodulin, Water Channel, MD Simulations
JOURNAL NAME:
Computational Molecular Bioscience,
Vol.6 No.4,
December
20,
2016
ABSTRACT: Aquaporin-0 (AQP0) contributes to the nurturing and cleaning of the eye lens of waste products. It is a tetrameric protein composed of four identical monomers, each of which has its own water pore. AQP0 water conduction is regulated by pH, Ca2+ concentration, and the phosphorylation of serine residues at the C-terminal. High cellular Ca2+ concentration enhances the binding of Calmodulin (CaM), a Ca2+ dependent protein, to AQP0 from cytoplasm. This study focuses on determining the differences between the AQP0-CaM and the open AQP0 systems, by using Molecular Dynamics (MD) methods. The water conduction energy profiles are measured with two separate MD simulation techniques revealed two distinct channel profiles for the AQP0-CaM combined model. While the CaM bound channels’ energy barriers exceed the 6 kcal/mol, the no CaM bound AQP0 energy profile stays below 3 kcal/mol. The structural analysis of these different pores during the free equilibrations also supported this conclusion with distinct pore diameters. Unlike the previous report, this study observed Phe75 and His66 taking role in stabilizing the CSII restriction site in CaM bound AQP0.