Five transmembrane core domain of YidC/Oxa1/Alb3 protein family of insertasesThe YidC/Oxa1/Alb3 protein family of insertases facilitate the insertion, folding and assembly of proteins of the inner membranes of bacteria and mitochondria, and the thylakoid membrane of plastids. Members include bacterial YidC, mitochondrial Cox18 and Oxa1, and chloroplastic Alb3 and Alb4. Membrane protein insertase YidC, also called foldase YidC or membrane integrase YidC, facilitates proper folding, insertion, and assembly of inner membrane proteins and complexes. Oxa1 and Cox18/Oxa2 mediate the insertion of both mitochondrion-encoded precursors and nuclear-encoded proteins from the matrix into the mitochondrial inner membrane. Alb3 and Alb3-like proteins, including Alb4, are required for the post-translational insertion of the light-harvesting chlorophyll-binding proteins (LHCPs) into the chloroplast thylakoid membrane. YidC/Oxa1/Alb3 family insertases contain a core domain of five transmembrane (5TM) segments that is essential to insertase function.