TCDB is operated by the Saier Lab Bioinformatics Group

1.A.74 The Mitsugumin 23 (MG23) Family

Mitsugumin 23 (MG23) is a 23 kDa transmembrane protein (homologous to the Bri3 protein) localized to the sarcoplasmic/endoplasmic reticulum and nuclear membranes in a wide variety of organisms and all types (Venturi et al., 2011). Venturi et al. (2011) reported the biochemical and biophysical characterization of MG23. Hydropathicity profile and limited proteolytic analysis proposed three - five transmembrane segments and a homo-oligomeric assembly. Ultrastructural observations detected a large symmetrical particle as the predominant component and a small asymmetric assembly as the second major component in purified MG23 preparations. Single-particle three-dimensional reconstruction revealed that MG23 forms a large bowl-shaped complex equipped with a putative central pore, which may be an assembly of the small asymmetric subunit. After reconstitution into planar phospholipid bilayers, purified MG23 behaved as a voltage-dependent, cation-conducting channel, permeable to both K+ and Ca2+. Multiple channels appeared to gate together. The bowl-shaped MG23 can transiently assemble and disassemble, allowing rapid cationic flux across intracellular membrane systems.

References associated with 1.A.74 family:

Matsuda, S., Y. Matsuda, and L. D''Adamio. (2009). BRI3 inhibits amyloid precursor protein processing in a mechanistically distinct manner from its homologue dementia gene BRI2. J. Biol. Chem. 284: 15815-15825. 19366692
Reilly-O''Donnell, B., G.B. Robertson, A. Karumbi, C. McIntyre, W. Bal, M. Nishi, H. Takeshima, A.J. Stewart, and S.J. Pitt. (2017). Dysregulated Zn2+ homeostasis impairs cardiac type-2 ryanodine receptor and mitsugumin 23 functions, leading to sarcoplasmic reticulum Ca2+ leakage. J. Biol. Chem. [Epub: Ahead of Print] 28630041
Takeshima, H., E. Venturi, and R. Sitsapesan. (2015). New and notable ion-channels in the sarcoplasmic/endoplasmic reticulum: do they support the process of intracellular Ca2+ release? J. Physiol. 593: 3241-3251. 26228553
Venturi, E., K. Mio, M. Nishi, T. Ogura, T. Moriya, S.J. Pitt, K. Okuda, S. Kakizawa, R. Sitsapesan, C. Sato, and H. Takeshima. (2011). Mitsugumin 23 forms a massive bowl-shaped assembly and cation-conducting channel. Biochemistry 50: 2623-2632. 21381722