Abstract

The Letm1 (leucine zipper-, EF hand-containing transmembrane protein 1) gene encodes a mitochondrial inner membrane protein, whose depletion severely perturbs mitochondrial Ca2+ and K+ homeostasis. Here we expressed, purified, and reconstituted human Letm1 protein in liposomes. Using Ca2+ fluorophore and 45Ca2+ based assays, we demonstrate directly that Letm1 is a Ca2+ transporter, with apparent affinities of cations in the sequence of Ca2+ ≈ Mn2+ > Gd3+ ≈ La3+ > Sr2+ >> Ba2+, Mg2+, K+, Na+. Kinetic analysis yields a Letm1 turnover rate of 2 Ca2+/s and Km of ∼25 μM. Further experiments show that Letm1 mediates electroneutral 1 Ca2+/2 H+ antiport. Letm1 is insensitive to ruthenium red (RR), an inhibitor of the mitochondrial calcium uniporter (MCU), and CGP-37157, an inhibitor of the mitochondrial Na+/Ca2+ exchanger. Functional properties of Letm1 described here are remarkably similar to those of the H+-dependent Ca2+ transport mechanism identified in intact mitochondria.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.