Binding of hydrogen-citrate to photoactive yellow protein is affected by the structural changes related to signaling state formation.
The tricarboxylic acid citric acid is a key intermediary metabolite in organisms from all domains of the tree of life. Surprisingly, this metabolite specifically interacts with the light-induced signaling state of the photoactive yellow protein (PYP), such that, at 30 mM, it retards recovery of this state to the stable ground state of the protein with up to 30%, in the range from pH 4.5 to pH 7. We have performed a detailed UV/vis spectroscopic study of the recovery of the signaling state of wild type (WT) PYP and two mutants, H108F and Δ25-PYP, derived from this protein, as a function of pH and the concentration of citric acid. This revealed that it is the dianionic form of citric acid that binds to the pB state of PYP. Its binding site is located in between the N-terminal cap and central β-sheet of PYP, which is accessible only in the signaling state of the protein. The obtained results show how changes in the distribution of subspecies of the signaling state of PYP influence the rate of ground state recovery.
Laboratory for Microbiology, Swammerdam Institute for Life Sciences and Netherlands Institute for Systems Biology, Amsterdam, The Netherlands.
Marijke
M
Hospes
Johannes H
JH
Ippel
Rolf
R
Boelens
Klaas J
KJ
Hellingwerf
Johnny
J
Hendriks
D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D019343:Citric Acid / Q000737:chemistry / Q000378:metabolism*; D020607:Halorhodospira halophila / Q000378:metabolism; D006859:Hydrogen / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D062105:Molecular Docking Simulation; D020283:Photoreceptors, Microbial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D013056:Spectrophotometry, Ultraviolet
D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; C050162:photoactive yellow protein, Bacteria; D019343:Citric Acid; D006859:Hydrogen