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PDBsum entry 2k2q
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Ligase/hydrolase
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PDB id
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2k2q
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References listed in PDB file
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Key reference
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Title
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Structural basis for the selectivity of the external thioesterase of the surfactin synthetase.
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Authors
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A.Koglin,
F.Löhr,
F.Bernhard,
V.V.Rogov,
D.P.Frueh,
E.R.Strieter,
M.R.Mofid,
P.Güntert,
G.Wagner,
C.T.Walsh,
M.A.Marahiel,
V.Dötsch.
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Ref.
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Nature, 2008,
454,
907-911.
[DOI no: ]
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PubMed id
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Abstract
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Non-ribosomal peptide synthetases (NRPS) and polyketide synthases (PKS) found in
bacteria, fungi and plants use two different types of thioesterases for the
production of highly active biological compounds. Type I thioesterases (TEI)
catalyse the release step from the assembly line of the final product where it
is transported from one reaction centre to the next as a thioester linked to a
4'-phosphopantetheine (4'-PP) cofactor that is covalently attached to thiolation
(T) domains. The second enzyme involved in the synthesis of these secondary
metabolites, the type II thioesterase (TEII), is a crucial repair enzyme for the
regeneration of functional 4'-PP cofactors of holo-T domains of NRPS and PKS
systems. Mispriming of 4'-PP cofactors by acetyl- and short-chain acyl-residues
interrupts the biosynthetic system. This repair reaction is very important,
because roughly 80% of CoA, the precursor of the 4'-PP cofactor, is acetylated
in bacteria. Here we report the three-dimensional structure of a type II
thioesterase from Bacillus subtilis free and in complex with a T domain.
Comparison with structures of TEI enzymes shows the basis for substrate
selectivity and the different modes of interaction of TEII and TEI enzymes with
T domains. Furthermore, we show that the TEII enzyme exists in several
conformations of which only one is selected on interaction with its native
substrate, a modified holo-T domain.
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Figure 1.
Figure 1: Assembly line of the surfactin non-ribosomal peptide
synthetase. The surfactin synthetase consists of the three
subunits SrfA-A, SrfA-B and SrfA-C that together comprise seven
modules, each being responsible for the incorporation of one
amino acid residue. The release of the lipoheptapeptide is
catalysed by TEI attached to SrfC (module 7). The function of
SrfD, the external thioesterase TEII (lower left), is the
recycling of misprimed T domains. The 4'-PP cofactor is depicted
shortened, attached to the T domains. Ac, acetyl.
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Figure 3.
Figure 3: Complex structure of SrfTEII and the TycC3 T domain.
a, Interaction surfaces (red) for SrfTEII (top) and the TycC3 T
domain (bottom) are based on chemical shift perturbations
observed in NMR titration experiments of ^15N-labelled Ser86Ala
SrfTEII with unlabelled acetyl-holo-T domain and vice versa. The
interaction surface identified on the T domain is identical to
results published previously^5. b, Ribbon diagram of the refined
average structure of the complex of SrfTEII and the TycC3 T
domain calculated using the simulated annealing protocol of
CNS1.1. Surfaces are displayed only for the residues of SrfTEII
(blue) and the TycC3 T domain (red) showing intermolecular NOEs.
Residues showing chemical shift changes are coloured in the
ribbon diagrams accordingly. Some of the active site residues of
the TEII triad (Ser 86 and His 216) and the modified T domain
active site (Ser 45-4'-PP) showed very severe line broadening
(Supplementary Figs 3 and 4). The position of the 4'-PP cofactor
shown is based on the position in the free H state of the TycC3
peptidyl carrier protein (TycC3–PCP)^5.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nature
(2008,
454,
907-911)
copyright 2008.
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