InterPro domain: IPR005689

Chloroplast function requires the import of nuclear encoded proteins from the cytoplasm across the chloroplast double membrane. This is accompished by two protein complexes, the Toc complex located at the outer membrane and the Tic complex loacted at the inner membrane [ 1 ]. The Toc complex recognises specific proteins by a cleavable N-terminal sequence and is primarily responsible for translocation through the outer membrane, while the Tic complex translocates the protein through the inner membrane.

This entry represents Toc750, a core component of the Toc complex. This protein is deeply embedded in the outer membrane and forms the voltage-dependent translocation channel [ 2 ]. Toc75 itself appears to be capable of at least some discrimination between substrate and non-substrate proteins, with recognition based on based on both conformational and electrostatic interactions.

1. Molecular biology of chloroplast biogenesis: gene expression, protein import and intraorganellar sorting. Cell. Mol. Life Sci. 58, 420-33
2. The chloroplast protein import channel Toc75: pore properties and interaction with transit peptides. Biophys. J. 83, 899-911