PDBsum entry 1csh

Lyase(oxo-acid)

PDB id: 1csh

Contents

Protein chain

435 a.a. *

Ligands

OAA

AMX

Waters ×145

* Residue conservation analysis

PDB id:

1csh

Name:

Lyase(oxo-acid)

Title:

A very short hydrogen bond provides only moderate stabilization of an enzyme: inhibitor complex of citrate synthase

Structure:

Citrate synthase. Chain: a. Engineered: yes

Source:

Gallus gallus. Chicken. Organism_taxid: 9031

Biol. unit:

Dimer (from PQS)

Resolution:

1.65Å R-factor: 0.164

Authors:

K.C.Usher,S.J.Remington

Key ref:

K.C.Usher et al. (1994). A very short hydrogen bond provides only moderate stabilization of an enzyme-inhibitor complex of citrate synthase. Biochemistry, 33, 7753-7759. PubMed id: 8011640 DOI: 10.1021/bi00191a002

Date:

07-Mar-94 Release date: 30-Apr-94

Protein chain

P23007  (CISY_CHICK) -  Citrate synthase, mitochondrial from Gallus gallus

Seq: 433 a.a.

Struc: 435 a.a.*

* PDB and UniProt seqs differ at 31 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.2.3.3.1 - citrate (Si)-synthase.
• Pathway: Citric acid cycle
• Reaction: oxaloacetate + acetyl-CoA + H2O = citrate + CoA + H⁺

oxaloacetate + acetyl-CoA + H2O (Bound ligand (Het Group name = OAA) corresponds exactly) = citrate + CoA (Bound ligand (Het Group name = AMX) matches with 90.38% similarity) + H(+)

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

reference

DOI no: 10.1021/bi00191a002

Biochemistry 33:7753-7759 (1994)

PubMed id: 8011640

A very short hydrogen bond provides only moderate stabilization of an enzyme-inhibitor complex of citrate synthase.

K.C.Usher, S.J.Remington, D.P.Martin, D.G.Drueckhammer.

ABSTRACT

Two extremely potent inhibitors of citrate synthase, carboxyl and primary amide analogues of acetyl coenzyme A, have been synthesized. The ternary complexes of these inhibitors with oxaloacetate and citrate synthase have been crystallized and their structures analyzed at 1.70- and 1.65-A resolution, respectively. The inhibitors have dissociation constants in the nanomolar range, with the carboxyl analogue binding more tightly (Ki = 1.6 nM at pH 6.0) than the amide analogue (28 nM), despite the unfavorable requirement for proton uptake by the former. The carboxyl group forms a shorter hydrogen bond with the catalytic Asp 375 (distance < 2.4 A) than does the amide group (distance approximately 2.5 A). Particularly with the carboxylate inhibitor, the very short hydrogen bond distances measured suggest a low barrier or short strong hydrogen bond. However, the binding constants differ by only a factor of 20 at pH 6.0, corresponding to an increase in binding energy for the carboxyl analogue on the enzyme of about 2 kcal/mol more than the amide analogue, much less than has been proposed for short strong hydrogen bonds based on gas phase measurements [> 20 kcal/mol (Gerlt & Gassman, 1993a,b)]. The inhibitor complexes support proposals that Asp 375 and His 274 work in concert to form an enolized form of acetyl-coenzyme A as the first step in the reaction.