Five transmembrane core domain of membrane protein insertase YidC, Alb3, and similar proteins
This group is composed of the bacterial and chloroplastic members of the YidC/Oxa1/Alb3 protein family of insertases, including bacterial YidC, and chloroplastic ALBINO3 (Alb3) and Alb3-like proteins such as ALBINO3-like protein 1 (also called 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. Depending on the nature of the substrate, YidC functions in a Sec-independent (YidC only) or a Sec-dependent manner as part of a complex containing YidC, the SecYEG channel, and SecDFYajC. YidC from Gram-negative bacteria contains an extra transmembrane segment (TM1) at the N-terminus and a large periplasmic domain, located between TM1 and TM2, that adopts a beta-super sandwich fold that is found in sugar-binding proteins such as galactose mutarotase. Alb3 and Alb3-like proteins are required for the post-translational insertion of the light-harvesting chlorophyll-binding proteins (LHCPs) into the chloroplast thylakoid membrane. Alb3 acts independently and may also function cooperatively with the thylakoid cpSecYE translocase to insert proteins co-translationally into the thylakoid membrane, similar to bacterial YidC that can function with the SecYEG translocase. YidC/Oxa1/Alb3 family insertases contain a core domain of five transmembrane (5TM) segments that is essential to insertase function.
Structure:5MG3: Escherichia coli YidC interacts with SecYEG protein-conducting channel and the accessory proteins SecDF-YajC to form the bacterial holo-translocon (HTL); contacts at 4A - View structure with Cn3D