Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 1976 Sep 25;251(18):5472-7.

Physical and chemical studies on bacterial superoxide dismutases. Purification and some anion binding properties of the iron-containing protein of Escherichia coli B

T O Slykhouse, J A Fee
  • PMID: 184081
Free article

Physical and chemical studies on bacterial superoxide dismutases. Purification and some anion binding properties of the iron-containing protein of Escherichia coli B

T O Slykhouse et al. J Biol Chem. .
Free article

Abstract

Highly purified iron superoxide dismutase was obtained from Escherichia coli B using a modification of the procedure of Yost and Jridovich (Yost, F. J., Jr., and Fridovich, I. (1973) J. Biol. Chem. 248, 4905-4908). The protein contained 1.8 +/- 0.2 atoms of iron per 38,700 g of protein. We have found that cyanide does not bind to the Fe3+ ion of iron dismutase but fluoride and azide have moderately large binding constants. Optical and electron paramagnetic resonance (EPR) measurements suggested that 2 fluoride ions could associate with each iron atom with the first having an association constant of approximately 520 M-1 and the second with an estimated value of 24 M-1. Activity measurements yielded an inhibition constant for fluoride of 30 M-1. At room temperature only one azide binds to the Fe3+ (K = 760 M-1) and this does not interfere with superoxide dismutase activity. Upon freezing solutions of iron superoxide dismutase in the presence of excess azide their color changes from yellow to pink. Combined EPR and optical titrations with azide suggest the presence of two binding sites on Fe3+ with only the first being occupied at room temperature and the second binding azide only upon freezing the solution. The results suggest that each Fe3+ ion of this superoxide dismutase has two coordination positions available for interaction with solute molecules but only one is necessary for catalysis of the superoxide dismutation reaction. The EPR, optical, and circular dichroism spectra of the native protein and the various fluoride and azide complexes are presented.

PubMed Disclaimer

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

Publication types

LinkOut - more resources