P89 HMP proliferation-inducing gene 4 MINOS2 PIG4 P87 Mic60 cell proliferation-inducing gene 4/52 protein mitochondrial inner membrane organizing system 2 MICOS complex subunit MIC60 motor protein PIG52 heart muscle protein mitochondrial contact site and cristae organizing system subunit 60 P87/89 cell proliferation-inducing protein 52 mitofilin mitochondrial inner membrane protein MICOS60