PDBsum entry 2bz3

Transferase

PDB id: 2bz3

Contents

Protein chains

406 a.a. *

Ligands

NH4 ×4

DAO ×4

SO4 ×2

Waters ×1022

* Residue conservation analysis

PDB id:

2bz3

Name:

Transferase

Title:

Structure of e.Coli kas i h298e mutant in complex with c12 fatty acid

Structure:

3-oxoacyl-[acyl-carrier-protein] synthase i. Chain: a, b, c, d. Synonym: beta-ketoacyl-acp synthase i, kas i. Engineered: yes. Mutation: yes. Other_details: thioester link from c163 to fatty acid ligand

Source:

Escherichia coli. Organism_taxid: 562. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dimer (from PDB file)

Resolution:

2.00Å R-factor: 0.196 R-free: 0.229

Authors:

J.G.Olsen,P.Von Wettstein-Knowles,A.Henriksen

Key ref:

P.von Wettstein-Knowles et al. (2006). Fatty acid synthesis. FEBS J, 273, 695-710. PubMed id: 16441657 DOI: 10.1111/j.1742-4658.2005.05101.x

Date:

10-Aug-05 Release date: 01-Feb-06

Protein chains

P0A953  (FABB_ECOLI) -  3-oxoacyl-[acyl-carrier-protein] synthase 1 from Escherichia coli (strain K12)

Seq: 406 a.a.

Struc: 406 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.2.3.1.41 - beta-ketoacyl-[acyl-carrier-protein] synthase I.
• Reaction: a fatty acyl-[ACP] + malonyl-[ACP] + H⁺ = a 3-oxoacyl-[ACP] + holo- [ACP] + CO2

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

Key reference

DOI no: 10.1111/j.1742-4658.2005.05101.x

FEBS J 273:695-710 (2006)

PubMed id: 16441657

Fatty acid synthesis.

P.von Wettstein-Knowles, J.G.Olsen, K.A.McGuire, A.Henriksen.

ABSTRACT

beta-Ketoacyl-acyl carrier protein (ACP) synthase enzymes join short carbon units to construct fatty acyl chains by a three-step Claisen condensation reaction. The reaction starts with a trans thioesterification of the acyl primer substrate from ACP to the enzyme. Subsequently, the donor substrate malonyl-ACP is decarboxylated to form a carbanion intermediate, which in the third step attacks C1 of the primer substrate giving rise to an elongated acyl chain. A subgroup of beta-ketoacyl-ACP synthases, including mitochondrial beta-ketoacyl-ACP synthase, bacterial plus plastid beta-ketoacyl-ACP synthases I and II, and a domain of human fatty acid synthase, have a Cys-His-His triad and also a completely conserved Lys in the active site. To examine the role of these residues in catalysis, H298Q, H298E and six K328 mutants of Escherichia colibeta-ketoacyl-ACP synthase I were constructed and their ability to carry out the trans thioesterification, decarboxylation and/or condensation steps of the reaction was ascertained. The crystal structures of wild-type and eight mutant enzymes with and/or without bound substrate were determined. The H298E enzyme shows residual decarboxylase activity in the pH range 6-8, whereas the H298Q enzyme appears to be completely decarboxylation deficient, showing that H298 serves as a catalytic base in the decarboxylation step. Lys328 has a dual role in catalysis: its charge influences acyl transfer to the active site Cys, and the steric restraint imposed on H333 is of critical importance for decarboxylation activity. This restraint makes H333 an obligate hydrogen bond donor at N(epsilon), directed only towards the active site and malonyl-ACP binding area in the fatty acid complex.

Selected figure(s)

Figure 1.
Fig. 1. Superimposition of the KAS I C163S-C12 (white, light colors) [3] and KAS I–C8 (gray, dark colors) active sites. Red spheres are water molecules. Blue atoms represent nitrogen, red represent oxygen, and green represents sulfur. Figures 1, 2 and 4 are made in MOLSCRIPT[41].

Figure 3.
Fig. 3. The active sites of the wild-type KAS I, its H298 mutants and their acyl complexes. (A) Wild-type. (B) WT–C8. (C) Superimposition of the wild-type (white, light colors) and H298E (orange, dark colors). (D) H298E. (E) H298E–C12. (F) H298Q. (G) H298Q–C12. (H) Superimposition of H298Q and H298Q–C12. In (A, B) and (D–G), water molecules (red spheres) within hydrogen bonding distance are indicated with dashed lines. (H) Superimposition of H298Q (orange, dark colors) and H298Q–C12 (white, light colors) not including water molecules. Figure prepared using PYMOL[42].

The above figures are reprinted by permission from the Federation of European Biochemical Societies: FEBS J (2006, 273, 695-710) copyright 2006.

Figures were selected by an automated process.