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PDBsum entry 2nq7
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References listed in PDB file
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Key reference
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Title
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Elucidation of the function of type 1 human methionine aminopeptidase during cell cycle progression.
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Authors
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X.Hu,
A.Addlagatta,
J.Lu,
B.W.Matthews,
J.O.Liu.
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Ref.
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Proc Natl Acad Sci U S A, 2006,
103,
18148-18153.
[DOI no: ]
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PubMed id
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Abstract
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Processing of the N-terminal initiator methionine is an essential cellular
process conserved from prokaryotes to eukaryotes. The enzymes that remove
N-terminal methionine are known as methionine aminopeptidases (MetAPs). Human
MetAP2 has been shown to be required for the proliferation of endothelial cells
and angiogenesis. The physiological function of MetAP1, however, has remained
elusive. In this report we demonstrate that a family of inhibitors with a core
structure of pyridine-2-carboxylic acid previously developed for the bacterial
and yeast MetAP1 is also specific for human MetAP1 (HsMetAP1), as confirmed by
both enzymatic assay and high-resolution x-ray crystallography. Treatment of
tumor cell lines with the MetAP1-specific inhibitors led to an accumulation of
cells in the G(2)/M phase, suggesting that HsMetAP1 may play an important role
in G(2)/M phase transition. Overexpression of HsMetAP1, but not HsMetAP2,
conferred resistance of cells to the inhibitors, and the inhibitors caused
retention of N-terminal methionine of a known MetAP substrate, suggesting that
HsMetAP1 is the cellular target for the inhibitors. In addition, when HsMetAP1
was knocked down by gene-specific siRNA, cells exhibited slower progression
during G(2)/M phase, a phenotype similar to cells treated with MetAP1
inhibitors. Importantly, MetAP1 inhibitors were able to induce apoptosis of
leukemia cell lines, presumably as a consequence of their interference with the
G(2)/M phase checkpoint. Together, these results suggest that MetAP1 plays an
important role in G(2)/M phase of the cell cycle and that it may serve as a
promising target for the discovery and development of new anticancer agents.
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Figure 1.
Fig. 1. Inhibition of MetAP by compound 1. Shown is
SDS/PAGE Western blot analysis of HeLa cells exposed to compound
1 at the indicated concentrations for 24 h. The membrane was
probed with a monoclonal antibody specific for the methionylated
14-3-3  (Upper) and tubulin
(Lower).
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Figure 5.
Fig. 5. Crystal structure of truncated HsMetAP1 in complex
with 1 and 2. (A) Superposed is the "omit" electron density map
shown in the inhibitor binding region of compounds 1 and 2.
Coefficients are (F[o] – F[c]), where the F[o] are the
observed structure amplitudes. The calculated amplitudes F[c]
and phases are obtained from the refined model with the
inhibitors removed. The maps calculated are at 1.5 Å
(contoured at 3.6  ) for 1 and at 1.6
Å (contoured at 3.6 ) for 2. (B) Stereo
diagram showing the superposition of enzyme-inhibitor complexes
of compounds 1 (green) and 2 (magenta) in the active site pocket
of the truncated HsMetAP1 (cyano). Note that both the compounds
use a third metal ion (Co^II) in binding to the protein. Except
for the contact through the metal ion, there are no obvious
hydrogen bond contacts between the protein and the inhibitors,
although they share several hydrophobic interactions. (C) Stereo
diagram of the superposed structures of HsMetAP1 in complex with
compounds 1 and 2 and HsMetAP2 (silver). Note that Tyr-444 of
the latter enzyme experiences a severe steric clash with the
side chains of compounds 1 and 2, explaining the lower affinity
of these compounds for HsMetAP2.
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