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bioRxiv · 10.1101/722926

Yeast Bax Inhibitor (Bxi1p/Ybh3p) is a Calcium Channel in E. coli

Mullin, J.·Kalhorn, J.·Mello, N.·Raffa, A.·Strakosha, A.·Austriaco, N.
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Abstract

Human Bax Inhibitor-1 (HsBI-1/TMBIM6) is the founding member of the evolutionary conserved TMBIM superfamily of proteins that share sequence homology within the transmembrane Bax inhibitor-containing motif (TMBIM). Mechanistically, BI-1/TMBIM6 and all the other mammalian TMBIM proteins appear to be involved in the maintenance of calcium homeostasis, and the crystal structure of a bacterial TMBIM protein, BsYetJ, suggests that the protein is a pH-sensitive calcium leak. The budding yeast, Saccharomyces cerevisiae, has a single TMBIM family member (YNL305C) named Bxi1p/Ybh3p. To determine the function of Bxi1p/Ybh3p, we overexpressed Bxi1p-EGFP in E. coli to determine if it is a calcium channel. We show that bacterial cells expressing Bxi1p-EGFP are more permeable to calcium than controls. Thus, our data suggests that yeast Bax inhibitor (Bxi1p) is a calcium channel in E. coli, lending support to our proposal that Bxi1p is a bona fide member of the TMBIM family of proteins. Further, we use our bacterial system to show that gadolinium is an inhibitor of Bxi1p in vivo, suggesting a path forward to identifying other small-molecular inhibitors of this clinically-important and highly conserved superfamily of proteins. Finally, parallel experiments revealed that the human Bax Inhibitor-1 (HsBI-1/TMBIM6) is also a calcium channel in bacteria that can be inhibited by gadolinium.

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Mullin, J., Kalhorn, J., Mello, N., Raffa, A., Strakosha, A., Austriaco, N.. 2019-08-02. Yeast Bax Inhibitor (Bxi1p/Ybh3p) is a Calcium Channel in E. coli. https://doi.org/10.1101/722926

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