Chlorophyll a with a farnesyl tail in thermophilic cyanobacteria
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Photosystem II (PSII) of oxygenic photosynthetic organisms normally contains exclusively chlorophyll a (Chl a) as its major light-harvesting pigment. Chl a canonically consists of the chlorin headgroup with a 20-carbon, 4-isoprene unit, phytyl tail. We have examined the 1.9 Å crystal structure of PSII from thermophilic cyanobacteria reported by Shen and coworkers in 2012 (PDB accession of 3ARC/3WU2). A newly refined electron density map from this structure, presented here, reveals that some assignments of the cofactors may be different from those modeled in the 3ARC/3WU2 structure, including a specific Chl a that appears to have a truncated tail by one isoprene unit. We provide experimental evidence using high-performance liquid chromatography and mass spectrometry for a small population of Chl a esterified to a 15-carbon farnesyl tail in PSII of thermophilic cyanobacteria.
KeywordsChlorophyll a CP43 Photosystem II Thermosynechococcus elongatus X-ray crystal structure
This work was funded by the Department of Energy Grant DE-FG02-05ER15646 (G.W.B.). Work in the laboratory of H.A.F. was supported by grants from the National Science Foundation (MCB-1243565) and the University of Connecticut Research Foundation. Crystallographic analysis of this study was in part funded by National Institutes of Health Program Grant P01 GM022779.
- Shen J-R, Kawakami K, Koike H (2010) Purification and crystallization of oxygen-evolving photosystem II core complex from thermophilic cyanobacteria. In: Carpentier R (ed) Photosynthesis research protocols, methods in molecular biology, vol 684. Humana Press, Totowa. doi: 10.1007/978-1-60761-925-3_5 Google Scholar