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Updated: Aug 23, 2026

Affinity Purification of Chloroplast Translocon Protein Complexes Using the TAP Tag
Published on: November 1, 2018
Toc12, a novel subunit of the intermembrane space preprotein translocon of chloroplasts
Thomas Becker1, Jozef Hritz, Markus Vogel
1Botanisches Institut, LMU München, 80638 Munich, Germany.
Abstract:
Translocation of proteins across membranes is essential for the biogenesis of each cell and is achieved by proteinaceous complexes. We analyzed the translocation complex of the intermembrane space from chloroplasts and identified a 12-kDa protein associated with the Toc machinery. Toc12 is an outer envelope protein exposing a soluble domain into the intermembrane space. Toc12 contains a J-domain and stimulates the ATPase activity of DnaK. The conformational stability and the ability to stimulate Hsp70 are dependent on a disulfide bridge within the loop region of the J-domain, suggesting a redox-regulated activation of the chaperone. Toc12 is associated with Toc64 and Tic22. Its J-domain recruits the Hsp70 of outer envelope membrane to the intermembrane space translocon and facilitates its interaction to the preprotein.
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