PDBsum entry 4n6b

Transferase

PDB id: 4n6b

Contents

Protein chains

(+ 0 more) 233 a.a.

Ligands

COA ×5

PDB id:

4n6b

Name:

Transferase

Title:

Soybean serine acetyltransferase complexed with coa

Structure:

Serine acetyltransferase apoenzyme. Chain: a, b, c, d, e, f. Engineered: yes

Source:

Glycine max. Soybeans. Organism_taxid: 3847. Expressed in: escherichia coli. Expression_system_taxid: 469008

Resolution:

3.01Å R-factor: 0.217 R-free: 0.268

Authors:

H.Yi,S.Dey,S.Kumaran,H.B.Krishnan,J.M.Jez

Key ref:

H.Yi et al. (2013). Structure of soybean serine acetyltransferase and formation of the cysteine regulatory complex as a molecular chaperone. J Biol Chem, 288, 36463-36472. PubMed id: 24225955 DOI: 10.1074/jbc.M113.527143

Date:

11-Oct-13 Release date: 13-Nov-13

Protein chains

I1KHY6  (I1KHY6_SOYBN) -  serine O-acetyltransferase from Glycine max

Seq: 286 a.a.

Struc: 233 a.a.*

* PDB and UniProt seqs differ at 10 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.2.3.1.30 - serine O-acetyltransferase.
• Reaction: L-serine + acetyl-CoA = O-acetyl-L-serine + CoA

L-serine + acetyl-CoA = O-acetyl-L-serine (Bound ligand (Het Group name = COA) corresponds exactly) + CoA

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1074/jbc.M113.527143

J Biol Chem 288:36463-36472 (2013)

PubMed id: 24225955

Structure of soybean serine acetyltransferase and formation of the cysteine regulatory complex as a molecular chaperone.

H.Yi, S.Dey, S.Kumaran, S.G.Lee, H.B.Krishnan, J.M.Jez.

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.