The PufX quinone channel enables the light‐harvesting 1 antenna to bind more carotenoids for light collection and photoprotection. Issue 4 (10th February 2017)

• Record Type: Journal Article
• Authors: Olsen, John D.; Martin, Elizabeth C.; Hunter, C. Neil
• Is Part Of: FEBS letters. Volume 591:Issue 4(2017)
• Page Start: 573
• Page End: 580
• Publication Date: 2017-02-10
• Subjects: bacterial photosynthesis -- carotenoid -- light‐harvesting -- membrane protein -- quinones, reaction centre; Biochemistry -- Periodicals; Biophysics -- Periodicals; Molecular biology -- Periodicals; Biochimie -- Périodiques; Biochemistry; Biophysics; Molecular biology; Periodicals; 572.05
• DOI: 10.1002/1873-3468.12575
• Languages: English
• ISSNs: 0014-5793

Abstract

Abstract : Photosynthesis in some phototrophic bacteria requires the PufX component of the reaction centre–light‐harvesting 1–PufX (RC‐LH1‐PufX) complex, which creates a pore for quinone/quinol (Q/QH2 ) exchange across the LH1 barrier surrounding the RC. However, photosynthetic bacteria such as Thermochromatium (T.) tepidum do not require PufX because there are fewer carotenoid binding sites, which creates multiple pores in the LH1 ring for Q/QH2 exchange. We show that an αTrp‐24 →Phe alteration of the Rhodobacter (Rba.) sphaeroides LH1 antenna impairs carotenoid binding and allows photosynthetic growth in the absence of PufX. We propose that acquisition of PufX and confining Q/QH2 traffic to a pore adjacent to the RC QB site is an evolutionary upgrade that allows increased LH1 carotenoid content for enhanced light absorption and photoprotection. Abstract : The PufX polypeptide is essential for photosynthesis in some bacteria. In other bacteria, Q/QH2 exchange across the low‐carotenoid LH1 barrier. A lower‐carotenoid LH1 allows photosynthesis in a Rba. sphaeroides PufX ‐ mutant. PufX creates a specialised zone for Q/QH2 exchange across the LH1 surrounding the RC. LH1 is now free to bind more carotenoids for light absorption and photoprotection.