PDBsum entry 1t3d

Transferase

PDB id: 1t3d

Contents

Protein chains

262 a.a. *

Ligands

CYS ×3

Waters ×416

* Residue conservation analysis

PDB id:

1t3d

Name:

Transferase

Title:

Crystal structure of serine acetyltransferase from e.Coli at 2.2a

Structure:

Serine acetyltransferase. Chain: a, b, c. Synonym: sat. Engineered: yes

Source:

Escherichia coli. Organism_taxid: 562. Gene: cyse, b3607, c4429, z5034, ecs4485, sf3646, s4122. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Hexamer (from PDB file)

Resolution:

2.20Å R-factor: 0.175 R-free: 0.177

Authors:

V.E.Pye,A.P.Tingey,R.L.Robson,P.C.E.Moody

Key ref:

V.E.Pye et al. (2004). The structure and mechanism of serine acetyltransferase from Escherichia coli. J Biol Chem, 279, 40729-40736. PubMed id: 15231846 DOI: 10.1074/jbc.M403751200

Date:

26-Apr-04 Release date: 13-Jul-04

Protein chains

P0A9D4  (CYSE_ECOLI) -  Serine acetyltransferase from Escherichia coli (strain K12)

Seq: 273 a.a.

Struc: 262 a.a.

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 (Bound ligand (Het Group name = CYS) matches with 75.00% similarity) = O-acetyl-L-serine + CoA

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

reference

DOI no: 10.1074/jbc.M403751200

J Biol Chem 279:40729-40736 (2004)

PubMed id: 15231846

The structure and mechanism of serine acetyltransferase from Escherichia coli.

V.E.Pye, A.P.Tingey, R.L.Robson, P.C.Moody.

ABSTRACT

Serine acetyltransferase (SAT) catalyzes the first step of cysteine synthesis in microorganisms and higher plants. Here we present the 2.2 A crystal structure of SAT from Escherichia coli, which is a dimer of trimers, in complex with cysteine. The SAT monomer consists of an amino-terminal alpha-helical domain and a carboxyl-terminal left-handed beta-helix. We identify His(158) and Asp(143) as essential residues that form a catalytic triad with the substrate for acetyl transfer. This structure shows the mechanism by which cysteine inhibits SAT activity and thus controls its own synthesis. Cysteine is found to bind at the serine substrate site and not the acetyl-CoA site that had been reported previously. On the basis of the geometry around the cysteine binding site, we are able to suggest a mechanism for the O-acetylation of serine by SAT. We also compare the structure of SAT with other left-handed beta-helical structures.

Selected figure(s)

Figure 3.
FIG. 3. The cysteine binding site and proposed mechanism. a, ball-and-stick representation of the cysteine (pink) binding pocket and key residues (one subunit, orange; adjacent subunit, blue). The main chain is solid-colored, and side chains are transparent; water molecules are represented as cyan spheres, and hydrogen bonds are represented as red dotted lines. b, stereoview of cysteine and water omit map (red) and 2Fo-Fc map of key residues, contoured at 1.2 . c, schematic representation of the proposed mechanism for O-acetylation of serine.

Figure 4.
FIG. 4. Comparison of left-handed -helical structures with SAT. a, serine acetytransferase; b, xenobiotic acetyltransferase (39% identity over 51 aa; Protein Data Bank code 2XAT [PDB] ); c, galactoside O-acetyltransferase (30% identity over 49 aa; Protein Data Bank code 1KRR [PDB] ); d, carbonic anhydrase (34.8% identity over 23 aa; Protein Data Bank code 1QRE [PDB] ); e, tetrahydrodipicilinate N-succinyltransferase (26% identity over 80 aa; Protein Data Bank code 3TDT [PDB] ); f, UDP-N-acetylglucosamine acyltransferase (32.1% identity over 53 aa; Protein Data Bank code 1J2Z [PDB] ). Structures are illustrated as C traces colored from amino terminus (red) to carboxyl terminus (blue).

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2004, 279, 40729-40736) copyright 2004.

Figures were selected by an automated process.