X-ray absorption studies of the Zn2+ site of glyoxalase I

L. Garcia-Iniguez, Linda S Powers, B. Chance, S. Sellin, B. Mannervik, A. S. Mildvan

Research output: Contribution to journalArticle

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Abstract

X-ray edge and extended absorption fine structure spectra of Zn2+ at the active site of glyoxalase I have been measured. The edge spectrum reveals a simple set of transitions consistent with a 7-coordinate or distorted octahedral Zn2+ model complex. Analysis of the fine structure rules out sulfur ligands to Zn2+ and yields a best fit complex with Zn2+-N (or Zn2+-O) distances of 2.04 and 2.10 Å, which are too great for tetrahedral Zn2+ coordination but are appropriate for an octahedral or more highly coordinated complex. Peaks of electron density in the Fourier-transformed region of the higher order shells at distances of 3-4 Å from the Zn2+ are similar to those found with known Zn2+-imidazole model complexes, including carbonic anhydrase [Yachandra, V., Powers, L., & Spiro, T. G. (1983) J. Am. Chem. Soc. 105, 6596-6604], indicating at least two imidazole ligands to Zn2+ on glyoxalase I. Binding of the heavy atom substrate analogue S-(p-bromobenzyl)glutathione did not significantly alter the number of atoms directly bonded to Zn2+ or their distances. No evidence for coordination of the cysteine sulfur of glutathione by the Zn2+ was obtained, and no heavy atom signal from bromine was detected, indicating this atom to be ≥4 Å from the Zn2+. However, conformational changes of the imidazole ligands of Zn2+ upon binding of the substrate analogue were suggested by changes in the relative intensity of the doublet peaks at 3-4 Å from the Zn2+ and assignable to imidazole. Thus, binding of the substrate analogue in the second coordination sphere may induce a small conformation change in the inner coordination sphere of Zn2+, possibly a rotation of the imidazole ligands.

Original languageEnglish (US)
Pages (from-to)685-689
Number of pages5
JournalBiochemistry
Volume23
Issue number4
StatePublished - 1984
Externally publishedYes

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Lactoylglutathione Lyase
X ray absorption
X-Rays
Ligands
Atoms
Sulfur
Carbonic Anhydrase V
Substrates
Bromine
Carrier concentration
Glutathione
Cysteine
Conformations
Catalytic Domain
imidazole
Electrons
X rays

ASJC Scopus subject areas

  • Biochemistry

Cite this

Garcia-Iniguez, L., Powers, L. S., Chance, B., Sellin, S., Mannervik, B., & Mildvan, A. S. (1984). X-ray absorption studies of the Zn2+ site of glyoxalase I. Biochemistry, 23(4), 685-689.

X-ray absorption studies of the Zn2+ site of glyoxalase I. / Garcia-Iniguez, L.; Powers, Linda S; Chance, B.; Sellin, S.; Mannervik, B.; Mildvan, A. S.

In: Biochemistry, Vol. 23, No. 4, 1984, p. 685-689.

Research output: Contribution to journalArticle

Garcia-Iniguez, L, Powers, LS, Chance, B, Sellin, S, Mannervik, B & Mildvan, AS 1984, 'X-ray absorption studies of the Zn2+ site of glyoxalase I', Biochemistry, vol. 23, no. 4, pp. 685-689.
Garcia-Iniguez L, Powers LS, Chance B, Sellin S, Mannervik B, Mildvan AS. X-ray absorption studies of the Zn2+ site of glyoxalase I. Biochemistry. 1984;23(4):685-689.
Garcia-Iniguez, L. ; Powers, Linda S ; Chance, B. ; Sellin, S. ; Mannervik, B. ; Mildvan, A. S. / X-ray absorption studies of the Zn2+ site of glyoxalase I. In: Biochemistry. 1984 ; Vol. 23, No. 4. pp. 685-689.
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AB - X-ray edge and extended absorption fine structure spectra of Zn2+ at the active site of glyoxalase I have been measured. The edge spectrum reveals a simple set of transitions consistent with a 7-coordinate or distorted octahedral Zn2+ model complex. Analysis of the fine structure rules out sulfur ligands to Zn2+ and yields a best fit complex with Zn2+-N (or Zn2+-O) distances of 2.04 and 2.10 Å, which are too great for tetrahedral Zn2+ coordination but are appropriate for an octahedral or more highly coordinated complex. Peaks of electron density in the Fourier-transformed region of the higher order shells at distances of 3-4 Å from the Zn2+ are similar to those found with known Zn2+-imidazole model complexes, including carbonic anhydrase [Yachandra, V., Powers, L., & Spiro, T. G. (1983) J. Am. Chem. Soc. 105, 6596-6604], indicating at least two imidazole ligands to Zn2+ on glyoxalase I. Binding of the heavy atom substrate analogue S-(p-bromobenzyl)glutathione did not significantly alter the number of atoms directly bonded to Zn2+ or their distances. No evidence for coordination of the cysteine sulfur of glutathione by the Zn2+ was obtained, and no heavy atom signal from bromine was detected, indicating this atom to be ≥4 Å from the Zn2+. However, conformational changes of the imidazole ligands of Zn2+ upon binding of the substrate analogue were suggested by changes in the relative intensity of the doublet peaks at 3-4 Å from the Zn2+ and assignable to imidazole. Thus, binding of the substrate analogue in the second coordination sphere may induce a small conformation change in the inner coordination sphere of Zn2+, possibly a rotation of the imidazole ligands.

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