Chloroplast protein precursors targeted to the outer membrane carry non-cleavable transit signals at their N-terminal end. Precursor proteins dock onto the TOC complex and translocate across the outer membrane. The TOC complex interacts with the TIC complex of the inner membrane and the TIC stromal components, forming a TOC-TIC super complex that helps the proteins move inwards. As the precursor enters the TIC complex, a polyglycine stretch close to the transit signal stalls further translocation, arresting the precursor at the TOC-TIC super complex. Plastidic type 1 signal peptidases cleave the polyglycine stretch while an N-terminal domain of the TOC complex, called the polypeptide transport-associated domain or POTRA domain, functions as a chaperone preventing precursor aggregation. The processed precursor is then transferred to an insertion pore complex called the outer membrane protein for integration into the chloroplast outer membrane.