Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

Mitsugumin 23 (MG23) is a 23 kDa transmembrane protein localized to the sarcoplasmic/endoplasmic reticulum and nuclear membranes in a wide variety of cells. Although the characteristics imply the participation in a fundamental function in intracellular membrane systems, the physiological role of MG23 is unknown. Here we report the biochemical and biophysical characterization of MG23. Hydropathicity profile and limited proteolytic analysis proposed three transmembrane segments in the MG23 primary structure. Chemical cross-linking analysis suggested a homo-oligomeric assembly of MG23. Ultrastructural observations detected a large symmetrical particle as the predominant component and a small asymmetric assembly as the second major component in highly purified MG23 preparations. Single-particle three-dimensional reconstruction revealed that MG23 forms a large bowl-shaped complex equipped with a putative central pore, which is considered 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 Ca(2+). A feature of MG23 gating was that multiple channels always appeared to be gating together in the bilayer. Our observations suggest that the bowl-shaped MG23 can transiently assemble and disassemble. These building transitions may underlie the unusual channel gating behavior of MG23 and allow rapid cationic flux across intracellular membrane systems.

Original publication

DOI

10.1021/bi1019447

Type

Journal article

Journal

Biochemistry

Publication Date

05/04/2011

Volume

50

Pages

2623 - 2632

Keywords

Animals, Calcium, Cross-Linking Reagents, Endoplasmic Reticulum, Humans, Hydrophobic and Hydrophilic Interactions, Imaging, Three-Dimensional, Ion Channels, Lipid Bilayers, Membrane Proteins, Microscopy, Electron, Peptide Fragments, Potassium, Protein Conformation, Protein Subunits, Rabbits, Recombinant Proteins, Sarcoplasmic Reticulum, Sequence Alignment, Sequence Homology, Amino Acid