Chlorophyll a with a farnesyl tail in thermophilic cyanobacteria

Photosynth Res. 2017 Nov;134(2):175-182. doi: 10.1007/s11120-017-0425-4. Epub 2017 Jul 24.


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.

Keywords: CP43; Chlorophyll a; Photosystem II; Thermosynechococcus elongatus; X-ray crystal structure.

MeSH terms

  • Chlorophyll / chemistry
  • Chlorophyll / metabolism*
  • Chlorophyll A
  • Cyanobacteria / physiology*
  • Electron Transport
  • Oxygen
  • Photosynthesis / physiology*
  • Photosystem II Protein Complex / metabolism*


  • Photosystem II Protein Complex
  • Chlorophyll
  • Oxygen
  • Chlorophyll A