Iron(III) coordination properties of a pyoverdin siderophore produced by Pseudomonas putida ATCC 33015.
The iron complexation of a fluorescent green pyoverdin siderophore produced by the environmental bacterium Pseudomonas putida was characterized by solution thermodynamic methods. Pyoverdin binds iron through three bidentate chelate groups, a catecholate, a hydroxamate, and an alpha-hydroxycarboxylic acid. The deprotonation constants of the free pyoverdin and Fe(III)-pyoverdin complex were determined through a series of potentiometric and spectrophotometric experiments. The ferric complex of pyoverdin forms at very low pH (pH < 2), but full iron coordination does not occur until neutral pH. The calculated pM value of 25.13 is slightly lower than that for pyoverdin PaA (pM = 27), which coordinates iron by a catecholate and two hydroxamate groups. The redox potential of Fe-pyoverdin was found to be very pH sensitive. At high pH (approximately pH 9-11) where pyoverdin coordinates Fe in a hexadentate mode the redox potential is -0.480 V (NHE); however, at neutral pH where full Fe coordination is incomplete, the redox potential is more positive (E(1/2) = -0.395 V). The positive shift in the redox potential and the partial dissociation of the Fe-pyoverdin complex with pH decrease provides a path toward in vivo iron release.
Boukhalfa
Hakim
H
Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Reilly
Sean D
SD
Michalczyk
Ryszard
R
Iyer
Srinivas
S
Neu
Mary P
MP
D005290:Ferric Compounds / Q000737:chemistry*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D009842:Oligopeptides / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D009942:Organometallic Compounds / Q000737:chemistry*; D011199:Potentiometry; D016958:Pseudomonas putida / Q000737:chemistry* / Q000378:metabolism; D017262:Siderophores / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013056:Spectrophotometry, Ultraviolet
D005290:Ferric Compounds; D009842:Oligopeptides; D009942:Organometallic Compounds; D017262:Siderophores; C042453:pyoverdin