The Arabidopsis thaliana protein ARTEMIS is an integral component of the chloroplast inner envelope required for chloroplast division. It contains a domain of significant homology to members of the Alb3/Oxa1/YidC protein family. Here, we show that upon expression in yeast mitochondria, ARTEMIS can partially take over the function of yeast Oxa1 in the insertion and assembly of mitochondrial membrane proteins. This identifies ARTEMIS as a functional member of the Alb3/Oxa1/YidC protein family and suggests the existence of a novel protein sorting pathway in chloroplasts which integrates polypeptides from the stroma into the inner envelope by an evolutionary conserved process.