Analysis of photosynthetic complexes from a cyanobacterial ycf37 mutant

Biochim Biophys Acta. 2006 Jan;1757(1):3-11. doi: 10.1016/j.bbabio.2005.11.001. Epub 2005 Dec 1.


The Ycf37 protein has been suggested to be involved in the biogenesis and/or stability of the cyanobacterial photosystem I (PSI). With Ycf37 specific antibodies, we analyzed the localization of Ycf37 within the thylakoid membranes of the cyanobacterium Synechocystis sp. PCC 6803. Inspection of a sucrose gradient profile indicated that small amounts of Ycf37 co-fractionated with monomeric photosynthetic complexes, but not with trimeric PSI. Isolating 3xFLAG epitope-tagged Ycf37 by affinity-tag purification rendered several PSI subunits that specifically co-precipitated with this protein. Blue-native PAGE newly revealed two monomeric PSI complexes (PSI and PSI*) in wild-type thylakoids. The lower amount of PsaK present in PSI* may explain its higher electrophoretic mobility. PSI* was more prominent in high-light grown cells and interestingly proved absent in the Deltaycf37 mutant. PSI* appeared again when the mutant was complemented in trans with the wild-type ycf37 gene. In the Deltaycf37 mutant the amount of trimeric PSI complexes was reduced to about 70% of the wild-type level with no significant changes in photochemical activity and subunit composition of the remaining photosystems. Our results indicate that Ycf37 plays a specific role in the preservation of PSI* and the biogenesis of PSI trimers.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / analysis*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Gene Deletion
  • Immunoprecipitation
  • Photosystem I Protein Complex / analysis*
  • Photosystem I Protein Complex / genetics
  • Photosystem I Protein Complex / metabolism*
  • Protein Subunits / analysis
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Synechocystis / enzymology*
  • Synechocystis / genetics
  • Thylakoids / enzymology*


  • Bacterial Proteins
  • Photosystem I Protein Complex
  • Protein Subunits
  • Ycf37 protein, Synechocystis