1MNQ

Thioesterase Domain of Picromycin Polyketide Synthase (PICS TE), pH 8.4

Summary for 1MNQ

• Entry DOI: 10.2210/pdb1mnq/pdb
• Related: 1KEZ 1MN6 1MNA 1MO0
• Descriptor: polyketide synthase IV (2 entities in total)
• Functional Keywords: thioesterase, polyketide synthase, open substrate channel, alpha-beta hydrolase, transferase
• Biological source: Streptomyces venezuelae
• Total number of polymer chains: 2
• Total formula weight: 62970.48

Authors

Tsai, S.-C.,Lu, H.,Cane, D.E.,Khosla, C.,Stroud, R.M. (deposition date: 2002-09-05, release date: 2003-02-04, Last modification date: 2024-02-14)

Primary citation

Tsai, S.-C.,Lu, H.,Cane, D.E.,Khosla, C.,Stroud, R.M.
Insights into channel architecture and substrate specificity from crystal structures of two macrocycle-forming thioesterases of modular polyketide synthases
Biochemistry, 41:12598-12606, 2002

PubMed Abstract: 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.

PubMed: 12379102
DOI: 10.1021/bi0260177

Experimental method

X-RAY DIFFRACTION (2.2 Å)