A gating mechanism of the BsYetJ calcium channel revealed in an endoplasmic reticulum lipid environment

• Published in: Biochimica et biophysica acta. Biomembranes Vol. 1865; no. 5; p. 184153
• Main Authors: Lan, Yu-Jing, Cheng, Chu-Chun, Chu, Shu-Chi, Chiang, Yun-Wei
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.06.2023
• Subjects: Apoptosis; Calcium - metabolism; Calcium channel; Calcium Channels; Electrochemical gradient; Endoplasmic reticulum; Endoplasmic Reticulum - metabolism; Fluorescence; Lipids; Membrane Proteins - chemistry; Proteoliposomes; Fluorescence; Calcium channel; Endoplasmic reticulum; Electrochemical gradient; Proteoliposomes; Apoptosis
• ISSN: 0005-2736; 1879-2642
• DOI: 10.1016/j.bbamem.2023.184153

The transmembrane BAX inhibitor-1-containing motif 6 (TMBIM6) is suggested to modulate apoptosis by regulating calcium homeostasis in the endoplasmic reticulum (ER). However, the precise molecular mechanism underlying this calcium regulation remains poorly understood. To shed light on this issue, we investigated all negatively charged residues in BsYetJ, a bacterial homolog of TMBIM6, using mutagenesis and fluorescence-based functional assays. We reconstituted BsYetJ in membrane vesicles with a lipid composition similar to that of the ER. Our results show that the charged residues E49 and R205 work together as a major gate, regulating calcium conductance in these ER-like lipid vesicles. However, these residues become largely inactive when reconstituted in other lipid environments. In addition, we found that D195 acts as a minor filter compared to the E49-R205 dyad. Our study uncovers a previously unknown function of BsYetJ/TMBIM6 in the calcium-dependent inactivation of BsYetJ, providing a framework for the development of a lipid-dependent mechanistic model of BsYetJ that will facilitate our understanding of calcium-dependent apoptosis. [Display omitted] •All negatively charged residues of BsYetJ are studied in ER-like lipid vesicles.•E49 and R205 act cooperatively as a major gate for calcium conductance.•D195 acts as a relatively minor filter compared to the E49-R205 dyad.•This study reveals calcium-dependent inactivation of BsYetJ.•We provide a framework for a lipid-dependent mechanistic model of BsYetJ.