 |
PDBsum entry 1fgh
|
|
|
|
References listed in PDB file
|
 |
|
Key reference
|
|
|
Title
|
|
The reaction of fluorocitrate with aconitase and the crystal structure of the enzyme-Inhibitor complex.
|
|
|
Authors
|
|
H.Lauble,
M.C.Kennedy,
M.H.Emptage,
H.Beinert,
C.D.Stout.
|
|
|
Ref.
|
|
Proc Natl Acad Sci U S A, 1996,
93,
13699-13703.
|
|
|
PubMed id
|
|
|
|
|
Note In the PDB file this reference is
annotated as "TO BE PUBLISHED".
The citation details given above were identified by an automated
search of PubMed on title and author
names, giving a
perfect match.
|
|
|
|
Abstract
|
|
|
It has been known for many years that fluoroacetate and fluorocitrate when
metabolized are highly toxic, and that at least one effect of fluorocitrate is
to inactivate aconitase. In this paper we present evidence supporting the
hypothesis that the (-)-erythro diastereomer of 2-fluorocitrate acts as a
mechanism based inhibitor of aconitase by first being converted to
fluoro-cis-aconitate, followed by addition of hydroxide and with loss of
fluoride to form 4-hydroxy-trans-aconitate (HTn), which binds very tightly, but
not covalently, to the enzyme. Formation of HTn by these reactions is in accord
with the working model for the enzyme mechanism. That HTn is the product of
fluorocitrate inhibition is supported by the crystal structure of the
enzyme-inhibitor complex at 2.05-A resolution, release of fluoride
stoichiometric with total enzyme when (-)-erythro-2-fluorocitrate is added, HPLC
analysis of the product, slow displacement of HTn by 10(6)-fold excess of
isocitrate, and previously published Mössbauer experiments. When
(+)-erythro-2-fluorocitrate is added to aconitase, the release of fluoride is
stoichiometric with total substrate added, and HPLC analysis of the products
indicates the formation of oxalosuccinate, and its derivative
alpha-ketoglutarate. This is consistent with the proposed mechanism, as is the
formation of HTn from (-)-erythro-2-fluorocitrate. The structure of the
inhibited complex reveals that HTn binds like the inhibitor trans-aconitate
while providing all the interactions of the natural substrate, isocitrate. The
structure exhibits four hydrogen bonds < 2.7 A in length involving HTn, H2O
bound to the [4Fe-4S] cluster, Asp-165 and His-167, as well as low temperature
factors for these moieties, consistent with the observed very tight binding of
the inhibitor.
|
|
|
|
|
|
|
