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PDBsum entry 1mo2
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Insights into channel architecture and substrate specificity from crystal structures of two macrocycle-Forming thioesterases of modular polyketide synthases.
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Authors
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S.C.Tsai,
H.Lu,
D.E.Cane,
C.Khosla,
R.M.Stroud.
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Ref.
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Biochemistry, 2002,
41,
12598-12606.
[DOI no: ]
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PubMed id
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Abstract
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Modular polyketide synthases (PKSs) synthesize the polyketide cores of
pharmacologically important natural products such as erythromycin and
picromycin. Understanding PKSs at high resolution could present new
opportunities for chemoenzymatic synthesis of complex molecules. The crystal
structures of macrocycle-forming thioesterase (TE) domains from the picromycin
synthase (PICS) and 6-deoxyerythronolide B synthase (DEBS) were determined to
1.8-3.0 A with an R(crys) of 19.2-24.4%, including three structures of PICS TE
(crystallized at pH 7.6, 8.0, and 8.4) and a second crystal form of DEBS TE. As
predicted by the previous work on DEBS TE [Tsai, S. C., et al. (2001) Proc.
Natl. Acad. Sci. U.S.A. 98, 14808-14813], PICS TE contains an open substrate
channel and a hydrophobic dimer interface. Notwithstanding their similarity, the
dimer interfaces and substrate channels of DEBS TE and PICS TE reveal key
differences. The structural basis for the divergent substrate specificities of
DEBS TE and PICS TE is analyzed. The size of the substrate channel increases
with increasing pH, presumably due to electrostatic repulsion in the channel at
elevated pH. Together, these structures support previous predictions that
macrocycle-forming thioesterases from PKSs share the same protein fold, an open
substrate channel, a similar catalytic mechanism, and a hydrophobic dimer
interface. They also provide a basis for the design of enzymes capable of
catalyzing regioselective macrocyclization of natural or synthetic substrates. A
series of high-resolution snapshots of a protein channel at different pHs is
presented alongside analysis of channel residues, which could help in the
redesign of the protein channel architecture.
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