Biochemical studies, Homology Modelling, and Molecular Docking of human Mitochondrial Calcium Uniporter (MCU) and the complex with Essential MCU Regulator (EMRE)

Abstract

The highly selective calcium uptake protein in the mitochondria (MCU) is a channel, which along with partner proteins like MICUs, MCUR1, and EMRE, senses cytosolic calcium levels and transports Ca2+ across the mitochondrial inner membrane into the matrix. Although absent in fungi, EMRE is essential in the interaction of MCU with MICU1 and MICU2 for the MCU-dependent calcium uptake. In this study, I focused on the biochemical studies of MCU-EMRE fusion complex and employed computational methods i.e. homology modeling and molecular docking to provide better insights into human mitochondrial uniporter complex. I have optimized the purification of the HsMCU-EMRE fusion recombinant proteins in the presence of LMPG and Fos-choline-14 detergents. Furthermore, I was able to exchange these said detergents with the surfactant, Amphipol A8-35, to enhance the probability of structure determination by crystallographic and cryo-EM techniques. Along with biochemical studies, I generated computational tetrameric HsMCU homology models based on the cryo-EM structures of fungal MCU published recently [1-4]. Moreover, I also generated models for HsMCU complexed with HsEMRE to visually define and characterize the interactions between MCU and EMRE consistent with the extensive biochemical studies done by Tsai et.al. [5]. My research thus provides an insight into the molecular mechanism of the human mitochondrial calcium uniporter complex.