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FEBS J. 2017 Sep;284(18):2981-2999. doi: 10.1111/febs.14163. Epub 2017 Aug 7.

Structure of the adenylation domain Thr1 involved in the biosynthesis of 4-chlorothreonine in Streptomyces sp. OH-5093-protein flexibility and molecular bases of substrate specificity.

Author information

1
Department of Biochemical Sciences "A. Rossi Fanelli", Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome, Italy.
2
Institute of Molecular Biology and Pathology, CNR - National Research Council of Italy, Rome, Italy.
3
Department of Biochemical Sciences "A. Rossi Fanelli", Sapienza University of Rome, Italy.

Abstract

We determined the crystal structure of Thr1, the self-standing adenylation domain involved in the nonribosomal-like biosynthesis of free 4-chlorothreonine in Streptomyces sp. OH-5093. Thr1 shows two monomers in the crystallographic asymmetric unit with different relative orientations of the C- and N-terminal subdomains both in the presence of substrates and in the unliganded form. Cocrystallization with substrates, adenosine 5'-triphosphate and l-threonine, yielded one monomer containing the two substrates and the other in complex with l-threonine adenylate, locked in a postadenylation state. Steady-state kinetics showed that Thr1 activates l-Thr and its stereoisomers, as well as d-Ala, l- and d-Ser, albeit with lower efficiency. Modeling of these substrates in the active site highlighted the molecular bases of substrate discrimination. This work provides the first crystal structure of a threonine-activating adenylation enzyme, a contribution to the studies on conformational rearrangement in adenylation domains and on substrate recognition in nonribosomal biosynthesis.

DATABASE:

Structural data are available in the Protein Data Bank under the accession number 5N9W and 5N9X.

KEYWORDS:

adenylation domain; crystallography; kinetic analysis; nonribosomal code; substrate specificity

PMID:
28704585
DOI:
10.1111/febs.14163
[Indexed for MEDLINE]
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