A Mechanistic Perspective on PEX1 and PEX6, Two AAA+ Proteins of the Peroxisomal Protein Import Machinery

In contrast to many protein translocases that use ATP or GTP hydrolysis as the driving force to transport proteins across biological membranes, the peroxisomal matrix protein import machinery relies on a regulated self-assembly mechanism for this purpose and uses ATP hydrolysis only to reset its components. The ATP-dependent protein complex in charge of resetting this machinery-the Receptor Export Module (REM)-comprises two members of the "ATPases Associated with diverse cellular Activities" (AAA+) family, PEX1 and PEX6, and a membrane protein that anchors the ATPases to the organelle membrane. In recent years, a large amount of data on the structure/function of the REM complex has become available. Here, we discuss the main findings and their mechanistic implications.