PT  - JOURNAL ARTICLE
AU  - Walter, Julia
AU  - Selim, Khaled A.
AU  - Leganés, Francisco
AU  - Fernández-Piñas, Francisca
AU  - Vothknecht, Ute C.
AU  - Forchhammer, Karl
AU  - Aro, Eva-Mari
AU  - Gollan, Peter J.
TI  - A novel Ca<sup>2+</sup>-binding protein influences photosynthetic electron transport in <em>Anabaena</em> sp. PCC 7120
AID  - 10.1101/571836
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 571836
4099  - http://biorxiv.org/content/early/2019/03/08/571836.short
4100  - http://biorxiv.org/content/early/2019/03/08/571836.full
AB  - Ca2+ is a potent signalling molecule that regulates many cellular processes. In cyanobacteria, Ca2+ has been linked to cell growth, stress response and photosynthesis, and to the development of specialist heterocyst cells in certain nitrogen-fixing species. Despite this, the pathways of calcium signal transduction in cyanobacteria are poorly understood, and only a few protein components are known. The current study describes a previously unreported calcium-binding protein which was called the Calcium Sensor EF-hand (CSE), which is conserved in filamentous, nitrogen-fixing cyanobacteria. CSE is shown to bind calcium, which induces a conformational change in the protein structure. Poor growth of a strain of Anabaena sp. PCC 7120 overexpressing CSE was attributed to diminished photosynthetic performance. Transcriptomics, biophysics and proteomics analyses revealed modifications in the light-harvesting phycobilisome and photosynthetic reaction center-protein complexes, and downregulated respiration.