Figure 1

LETM1 is responsible for mitochondrial Ca²⁺ output.

(A) Putative domain organization of LETM1. (B) Protease K digestion of LETM1 in mitochondria. The mitochondria were isolated from cells that overexpressed LETM1 and were incubated with increasing concentrations of digitonin in the presence of Protease K. The samples were analyzed using western blotting. An inner membrane protein TIM23, a mitochondrial matrix protein PRX3 and HA-LETM1 were tested. The HA tag position in LETM1 is indicated. (C) Schematic representation of the LETM1 localization on the inner mitochondrial membrane. The N-terminus of LETM1 is located on the mitochondrial intermembrane space and the C-terminus extends into the matrix. The orange sphere represents Ca²⁺. (D) Responses of the mitochondrial Ca²⁺ level in LETM1 knockdown HeLa cells after stimulation of 100 μM of histamine. (E) Western blot analysis of LETM1 protein levels in HeLa cells. Full gel and blots were shown in Figure S4. (F) Quantify human LETM1 protein levels only in HeLa cells by integrated density.