title: Expression and preliminary characterization of human MICU2.
abstract: MICU2 has been reported to interact with MICU1 and participate in the regulation of mitochondrial Ca(2+) uptake, although the molecular determinants underlying the function of MICU2 is unknown. In order to characterize MICU2 we screened a series of N-terminal and C-terminal truncations and obtained constructs which can be expressed in abundance, giving rise to soluble samples to enable subsequent characterizations. Size exclusion chromatography (SEC) and multi-angle laser light scattering (MALLS) revealed that MICU2 exists as a monomer in Ca(2+)-free conditions but forms a dimer in Ca(2+)-bound conditions. Unlike MICU1, the C-helix domain of MICU2 exhibits no influence on protein conformation in both Ca(2+)-free and Ca(2+)-bound forms. Furthermore, mutation of the first EF-hand abolishes the ability of MICU2 to switch to a dimer in the presence of Ca(2+), indicating that the first EF-hand is not only involved in Ca(2+) binding but also in conformational change. Our pull-down and co-immunoprecipitation assays suggest that, in addition to disulfide bonds, salt bridges also contribute to MICU1-MICU2 heterodimer formation.
authors.affiliation: College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.affiliation: College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Wenping
authors.initials: W
authors.lastname: Wu
authors.affiliation: College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Hairun
authors.initials: H
authors.lastname: Pei
authors.affiliation: College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Wei
authors.affiliation: College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Qingzhan
authors.initials: Q
authors.lastname: Yang
authors.affiliation: College of Chemistry, Beijing Normal University, Beijing 100875, China jimin_z@bnu.edu.cn jia@queensu.ca.
authors.forename: Jimin
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Department of Biochemical and Molecular Science, Queen University, Kingston, Ontario, Canada K7L 3N6 jimin_z@bnu.edu.cn jia@queensu.ca.
authors.forename: Zongchao
authors.identifier: http://orcid.org/0000-0002-9322-9394
authors.initials: Z
authors.lastname: Jia
keywords: Calcium; EF-hand; MICU1; MICU2; Mitochondria