Izvorni znanstveni članak

https://doi.org/10.18054/pb.2015.117.3.1002

Chloroplast signal length requirement reflects the outer membrane and TOC complex dimension

Bodo Tilman ; Molecular Cell Biology of Plants, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany; TRON - Translational Oncology at the University Medical Center of the Johannes Gutenberg University Mainz GmbH
Oliver Mirus ; Molecular Cell Biology of Plants, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
Enrico Schleiff ; Molecular Cell Biology of Plants, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany; Cluster of Excellence Frankfurt; Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany; Buchmann Institute for Molecular Life Sciences; Goethe U

Sažetak

Background and Purpose: The evolution of an efficient preprotein targeting and translocation system was a central prerequisite for the endosymbiotic integration of a-proteobacteria and cyanobacteria as cellular organelles.
Today, it is widely accepted that during evolution most (pre-)proteins
destined for these two organelles were equipped with an N-terminal targeting signal for localization. While multiple modes of evolution of these extensions are currently discussed, all evolved signals serve the same function – forming a signal for targeting to the correct organelle and translocation across both membranes. We aimed to generalize the current idea for the length requirement of the N-terminal extension for efficient translocation.
Methods: To explore translocation efficiency in vivo we used protoplasts isolated from different plant sources. We compared the behavior of native and artificial precursor proteins in this plant cell system by fluorescence microscopy.
Results: We demonstrate that the minimal length of the N-terminal
amino acid stretch in a loosely folded conformation of a precursor of a chloroplast protein is about 60 amino acid residues. This amino acid stretch in a loosely folded state is prerequisite that a preprotein can traverse the outer membrane in vivo.
Conclusion: We generalize the evidence that two distinct prerequisites
framed the evolutionary process of development of targeting signals for chloroplast translocation. (i) The emerging signal had to be sufficiently distinct to signals existing for targeting to other cellular compartments. (ii) The N-terminal signal had to evolve with physico-chemical properties that serve both purposes: targeting and translocation. With respect to the latter, the length of the unfolded polypeptide is defined by the dimension of the translocon and the resulting distance between the cytosolically exposed receptors
acting on the cis side of the membrane and the molecular machinery energizing translocation acting in trans – in the intermembrane space.

Ključne riječi

Protein translocation; targeting signal; transit peptide; chloroplast; TOC translocon

Hrčak ID:

151191

URI

https://hrcak.srce.hr/151191

Datum izdavanja:

30.11.2015.

Posjeta: 1.449 *