A protease-mediated mechanism regulates the cytochrome <i>c</i> <sub>6</sub> /plastocyanin switch in <i>Synechocystis</i> sp. PCC 6803
Raquel García-Cañas, Joaquín Giner‐Lamia, Francisco J. Florencio, Luis López‐Maury
Abstract
Significance After the appearance of oxygenic photosynthesis, iron (Fe) became oxidized, and its solubility and availability were greatly decreased. This generated a problem for most organisms since they are strongly dependent on Fe, especially photosynthetic organisms. In response, organisms evolved alternatives to Fe-containing proteins such as plastocyanin, a copper protein that substitutes for cytochrome c 6 in photosynthesis. Expression of these two proteins in cyanobacteria is regulated by Cu availability, but the regulatory system remains unknown. Herein, we describe the regulatory system for these alternative proteins in photosynthesis in cyanobacteria. The mechanism involves a transcription factor (PetR) and a membrane protease (PetP) that degrades PetR in the presence of Cu.