4N69

Soybean Serine Acetyltransferase Complexed with Serine

Summary for 4N69

• Entry DOI: 10.2210/pdb4n69/pdb
• Related: 4N6A 4N6B
• Descriptor: Serine Acetyltransferase Apoenzyme, SERINE, PHOSPHATE ION, ... (4 entities in total)
• Functional Keywords: acetyltransferase, transferase
• Biological source: Glycine max (soybeans)
• Total number of polymer chains: 2
• Total formula weight: 61203.34

Authors

Yi, H.,Dey, S.,Kumaran, S.,Krishnan, H.B.,Jez, J.M. (deposition date: 2013-10-11, release date: 2013-11-13, Last modification date: 2024-02-28)

Primary citation

Yi, H.,Dey, S.,Kumaran, S.,Lee, S.G.,Krishnan, H.B.,Jez, J.M.
Structure of soybean serine acetyltransferase and formation of the cysteine regulatory complex as a molecular chaperone.
J.Biol.Chem., 288:36463-36472, 2013

PubMed Abstract: Serine acetyltransferase (SAT) catalyzes the limiting reaction in plant and microbial biosynthesis of cysteine. In addition to its enzymatic function, SAT forms a macromolecular complex with O-acetylserine sulfhydrylase. Formation of the cysteine regulatory complex (CRC) is a critical biochemical control feature in plant sulfur metabolism. Here we present the 1.75-3.0 Å resolution x-ray crystal structures of soybean (Glycine max) SAT (GmSAT) in apoenzyme, serine-bound, and CoA-bound forms. The GmSAT-serine and GmSAT-CoA structures provide new details on substrate interactions in the active site. The crystal structures and analysis of site-directed mutants suggest that His(169) and Asp(154) form a catalytic dyad for general base catalysis and that His(189) may stabilize the oxyanion reaction intermediate. Glu(177) helps to position Arg(203) and His(204) and the β1c-β2c loop for serine binding. A similar role for ionic interactions formed by Lys(230) is required for CoA binding. The GmSAT structures also identify Arg(253) as important for the enhanced catalytic efficiency of SAT in the CRC and suggest that movement of the residue may stabilize CoA binding in the macromolecular complex. Differences in the effect of cold on GmSAT activity in the isolated enzyme versus the enzyme in the CRC were also observed. A role for CRC formation as a molecular chaperone to maintain SAT activity in response to an environmental stress is proposed for this multienzyme complex in plants.

PubMed: 24225955
DOI: 10.1074/jbc.M113.527143

Experimental method

X-RAY DIFFRACTION (1.8 Å)