Essential component of the TIM23 complex, a complex that mediates the translocation of transit peptide-containing proteins across the mitochondrial inner membrane. Has some phosphatase activity in vitro; however such activity may not be relevant in vivo. Component of the TIM23 complex at least composed of TIMM23, TIMM17 (TIMM17A or TIMM17B) and TIMM50; within this complex, directly interacts with TIMM23. The complex interacts with the TIMM44 component of the PAM complex and with DNAJC15. Belongs to the TIM50 family.