3IAU

The structure of the processed form of threonine deaminase isoform 2 from Solanum lycopersicum

Summary for 3IAU

• Entry DOI: 10.2210/pdb3iau/pdb
• Descriptor: Threonine deaminase, SULFATE ION, POLYETHYLENE GLYCOL (N=34), ... (5 entities in total)
• Functional Keywords: pyridoxal phosphate, amino-acid biosynthesis, defensive protein, jasmonic acid pathway, jasmonic acid, structural genomics, protein structure initiative, psi, center for eukaryotic structural genomics, cesg, allosteric enzyme, branched-chain amino acid biosynthesis, chloroplast, isoleucine biosynthesis, lyase, transit peptide
• Biological source: Solanum lycopersicum (tomato)
• Cellular location: Plastid, chloroplast: P25306
• Total number of polymer chains: 2
• Total formula weight: 80118.28

Authors

Bianchetti, C.M.,Bingman, C.A.,Phillips Jr., G.N.,Center for Eukaryotic Structural Genomics (CESG) (deposition date: 2009-07-14, release date: 2009-07-28, Last modification date: 2025-03-26)

Primary citation

Gonzales-Vigil, E.,Bianchetti, C.M.,Phillips, G.N.,Howe, G.A.
Adaptive evolution of threonine deaminase in plant defense against insect herbivores.
Proc.Natl.Acad.Sci.USA, 108:5897-5902, 2011

PubMed Abstract: Gene duplication is a major source of plant chemical diversity that mediates plant-herbivore interactions. There is little direct evidence, however, that novel chemical traits arising from gene duplication reduce herbivory. Higher plants use threonine deaminase (TD) to catalyze the dehydration of threonine (Thr) to α-ketobutyrate and ammonia as the committed step in the biosynthesis of isoleucine (Ile). Cultivated tomato and related Solanum species contain a duplicated TD paralog (TD2) that is coexpressed with a suite of genes involved in herbivore resistance. Analysis of TD2-deficient tomato lines showed that TD2 has a defensive function related to Thr catabolism in the gut of lepidopteran herbivores. During herbivory, the regulatory domain of TD2 is removed by proteolysis to generate a truncated protein (pTD2) that efficiently degrades Thr without being inhibited by Ile. We show that this proteolytic activation step occurs in the gut of lepidopteran but not coleopteran herbivores, and is catalyzed by a chymotrypsin-like protease of insect origin. Analysis of purified recombinant enzymes showed that TD2 is remarkably more resistant to proteolysis and high temperature than the ancestral TD1 isoform. The crystal structure of pTD2 provided evidence that electrostatic interactions constitute a stabilizing feature associated with adaptation of TD2 to the extreme environment of the lepidopteran gut. These findings demonstrate a role for gene duplication in the evolution of a plant defense that targets and co-opts herbivore digestive physiology.

PubMed: 21436043
DOI: 10.1073/pnas.1016157108

Experimental method

X-RAY DIFFRACTION (2.353 Å)