Co-operation between different targeting pathways during integration of a membrane protein |
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| Authors: | Rebecca Keller Jeanine de Keyzer Arnold JM Driessen Tracy Palmer |
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| Institution: | 1Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK;2Divison of Molecular Microbiology Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, Netherlands |
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| Abstract: | Membrane protein assembly is a fundamental process in all cells. The membrane-bound Rieske iron-sulfur protein is an essential component of the cytochrome bc1 and cytochrome b6f complexes, and it is exported across the energy-coupling membranes of bacteria and plants in a folded conformation by the twin arginine protein transport pathway (Tat) transport pathway. Although the Rieske protein in most organisms is a monotopic membrane protein, in actinobacteria, it is a polytopic protein with three transmembrane domains. In this work, we show that the Rieske protein of Streptomyces coelicolor requires both the Sec and the Tat pathways for its assembly. Genetic and biochemical approaches revealed that the initial two transmembrane domains were integrated into the membrane in a Sec-dependent manner, whereas integration of the third transmembrane domain, and thus the correct orientation of the iron-sulfur domain, required the activity of the Tat translocase. This work reveals an unprecedented co-operation between the mechanistically distinct Sec and Tat systems in the assembly of a single integral membrane protein. |
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