Structural basis for a pH-sensitive calcium leak across membranes.Chang, Y., Bruni, R., Kloss, B., Assur, Z., Kloppmann, E., Rost, B., Hendrickson, W.A., Liu, Q.
(2014) Science 344: 1131-1135
- PubMed: 24904158
- DOI: 10.1126/science.1252043
- Primary Citation of Related Structures:
4PGU, 4PGV, 4PGW, 4PGR, 4PGS
- PubMed Abstract:
Calcium homeostasis balances passive calcium leak and active calcium uptake. Human Bax inhibitor-1 (hBI-1) is an antiapoptotic protein that mediates a calcium leak and is representative of a highly conserved and widely distributed family, the transme ...
Calcium homeostasis balances passive calcium leak and active calcium uptake. Human Bax inhibitor-1 (hBI-1) is an antiapoptotic protein that mediates a calcium leak and is representative of a highly conserved and widely distributed family, the transmembrane Bax inhibitor motif (TMBIM) proteins. Here, we present crystal structures of a bacterial homolog and characterize its calcium leak activity. The structure has a seven-transmembrane-helix fold that features two triple-helix sandwiches wrapped around a central C-terminal helix. Structures obtained in closed and open conformations are reversibly interconvertible by change of pH. A hydrogen-bonded, pKa (where Ka is the acid dissociation constant)-perturbed pair of conserved aspartate residues explains the pH dependence of this transition, and biochemical studies show that pH regulates calcium influx in proteoliposomes. Homology models for hBI-1 provide insights into TMBIM-mediated calcium leak and cytoprotective activity.
New York Consortium on Membrane Protein Structure, New York Structural Biology Center, New York, NY 10027, USA. New York Structural Biology Center, National Synchrotron Light Source (NSLS) X4, Brookhaven National Laboratory, Upton, NY 11973, USA. firstname.lastname@example.org.