Essential component of the TIM23 complex, a complex that mediates the translocation of transit peptide-containing proteins across the mitochondrial inner membrane. Component of the TIM23 complex at least composed of TIMM23, TIMM17 (TIMM17A or TIMM17B) and TIMM50; within this complex, directly interacts with TIMM50. The complex interacts with the TIMM44 component of the PAM complex and with DNAJC15. Belongs to the Tim17/Tim22/Tim23 family.