Kinetics of iron acquisition from ferric siderophores by Paracoccus denitrificans

Journal Article · Tue May 01 04:00:00 EDT 1990 · Journal of Bacteriology; (USA)

OSTI ID:6809821

Bergeron, R J; Weimar, W R ^[1]

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1. Univ. of Florida, Gainesville (USA)

The kinetics of iron accumulation by iron-starved Paracoccus denitrificans during the first 2 min of exposure to 55Fe-labeled ferric siderophore chelates is described. Iron is acquired from the ferric chelate of the natural siderophore L-parabactin in a process exhibiting biphastic kinetics by Lineweaver-Burk analysis. The kinetic data for 1 microM less than (Fe L-parabactin) less than 10 microM fit a regression line which suggests a low-affinity system (Km = 3.9 +/- 1.2 microM, Vmax = 494 pg-atoms of 55Fe min-1 mg of protein-1), whereas the data for 0.1 microM less than or equal to (Fe L-parabactin) less than or equal to 1 microM fit another line consistent with a high-affinity system (Km = 0.24 +/- 0.06 microM, Vmax = 108 pg-atoms of 55Fe min-1 mg of protein-1). The Km of the high-affinity uptake is comparable to the binding affinity we had previously reported for the purified ferric L-parabactin receptor protein in the outer membrane. In marked contrast, ferric D-parabactin data fit a single regression line corresponding to a simple Michaelis-Menten process with comparatively low affinity (Km = 3.1 +/- 0.9 microM, Vmax = 125 pg-atoms of 55Fe min-1 mg of protein-1). Other catecholamide siderophores with an intact oxazoline ring derived from L-threonine (L-homoparabactin, L-agrobactin, and L-vibriobactin) also exhibit biphasic kinetics with a high-affinity component similar to ferric L-parabactin. Circular dichroism confirmed that these ferric chelates, like ferric L-parabactin, exist as the lambda enantiomers.

• OSTI ID: 6809821
• Journal Information: Journal of Bacteriology; (USA), Journal Name: Journal of Bacteriology; (USA) Vol. 172:5; ISSN JOBAA; ISSN 0021-9193
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BETA DECAY RADIOISOTOPES
BIOLOGICAL ACCUMULATION
CELL CONSTITUENTS
CELL MEMBRANES
CHELATING AGENTS
DICHROISM
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTS
EVEN-ODD NUCLEI
INTERMEDIATE MASS NUCLEI
IRON
IRON 55
IRON ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPE DILUTION
ISOTOPES
MAGNETIC CIRCULAR DICHROISM
MEMBRANE TRANSPORT
MEMBRANES
METABOLISM
METALS
MOLECULAR STRUCTURE
NUCLEI
RADIOISOTOPES
TRACER TECHNIQUES
TRANSITION ELEMENTS
YEARS LIVING RADIOISOTOPES