3VC3

Crystal structure of beta-cyanoalanine synthase K95A mutant in soybean

Summary for 3VC3

• Entry DOI: 10.2210/pdb3vc3/pdb
• Related: 3VBE
• Descriptor: beta-cyanoalnine synthase, N-({3-HYDROXY-2-METHYL-5-[(PHOSPHONOOXY)METHYL]PYRIDIN-4-YL}METHYL)-L-CYSTEINE (3 entities in total)
• Functional Keywords: beta-cyanoalanine synthase, transferase
• Biological source: Glycine max (soybeans)
• Total number of polymer chains: 6
• Total formula weight: 225184.22

Authors

Yi, H.,Jez, J.M. (deposition date: 2012-01-03, release date: 2012-09-12, Last modification date: 2024-02-28)

Primary citation

Yi, H.,Juergens, M.,Jez, J.M.
Structure of Soybean beta-Cyanoalanine Synthase and the Molecular Basis for Cyanide Detoxification in Plants.
Plant Cell, 24:2696-2706, 2012

PubMed Abstract: Plants produce cyanide (CN-) during ethylene biosynthesis in the mitochondria and require β-cyanoalanine synthase (CAS) for CN- detoxification. Recent studies show that CAS is a member of the β-substituted alanine synthase (BSAS) family, which also includes the Cys biosynthesis enzyme O-acetylserine sulfhydrylase (OASS), but how the BSAS evolved distinct metabolic functions is not understood. Here we show that soybean (Glycine max) CAS and OASS form α-aminoacrylate reaction intermediates from Cys and O-acetylserine, respectively. To understand the molecular evolution of CAS and OASS in the BSAS enzyme family, the crystal structures of Gm-CAS and the Gm-CAS K95A mutant with a linked pyridoxal phosphate (PLP)-Cys molecule in the active site were determined. These structures establish a common fold for the plant BSAS family and reveal a substrate-induced conformational change that encloses the active site for catalysis. Comparison of CAS and OASS identified residues that covary in the PLP binding site. The Gm-OASS T81M, S181M, and T185S mutants altered the ratio of OASS:CAS activity but did not convert substrate preference to that of a CAS. Generation of a triple mutant Gm-OASS successfully switched reaction chemistry to that of a CAS. This study provides new molecular insight into the evolution of diverse enzyme functions across the BSAS family in plants.

PubMed: 22739827
DOI: 10.1105/tpc.112.098954

Experimental method

X-RAY DIFFRACTION (1.766 Å)