Probably involved in mitochondrial protein import. Is also required for efficient translocation of pre-pro-alpha-factor. Involved in heme regulation of HAP1, as a component of the high-molecular-weight (HMC) complex. Homodimer. Interacts with HAP1. Component of the HMC including HAP1, SRO9 and YDJ1. Concentrated in a perinuclear ring as well as in the cytoplasm. YDJ1 is a heat shock gene whose expression increases moderately at elevated temperatures. Present with 119000 molecules/cell in log phase SD medium.