PDBsum entry 1a59

Cold-activity

PDB id: 1a59

Contents

Protein chain

377 a.a. *

Ligands

COA

CIT

* Residue conservation analysis

PDB id:

1a59

Name:

Cold-activity

Title:

Cold-active citrate synthase

Structure:

Citrate synthase. Chain: a. Engineered: yes

Source:

Antarctic bacterium ds2-3r. Organism_taxid: 56673. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dimer (from PDB file)

Resolution:

2.09Å R-factor: 0.184 R-free: 0.236

Authors:

R.J.M.Russell,U.Gerike,M.J.Danson,D.W.Hough,G.L.Taylor

Key ref:

R.J.Russell et al. (1998). Structural adaptations of the cold-active citrate synthase from an Antarctic bacterium. Structure, 6, 351-361. PubMed id: 9551556 DOI: 10.1016/S0969-2126(98)00037-9

Date:

20-Feb-98 Release date: 30-Mar-99

Protein chain

O34002  (PRPC_ABDS2) -  2-methylcitrate synthase from Antarctic bacterium DS2-3R

Seq: 379 a.a.

Struc: 377 a.a.

Enzyme reactions

• Enzyme class 1: E.C.2.3.3.16 - citrate synthase (unknown stereospecificity).
• Reaction: oxaloacetate + acetyl-CoA + H2O = citrate + CoA + H⁺

oxaloacetate + acetyl-CoA + H2O = citrate (Bound ligand (Het Group name = CIT) corresponds exactly) + CoA (Bound ligand (Het Group name = COA) matches with 95.83% similarity) + H(+)

• Enzyme class 2: E.C.2.3.3.5 - 2-methylcitrate synthase.

Pathway:

• Reaction: propanoyl-CoA + oxaloacetate + H2O = (2S,3S)-2-methylcitrate + CoA + H⁺

propanoyl-CoA + oxaloacetate (Bound ligand (Het Group name = CIT) matches with 69.23% similarity) + H2O = (2S,3S)-2-methylcitrate + CoA (Bound ligand (Het Group name = COA) matches with 95.83% similarity) + H(+)

Note, where more than one E.C. class is given (as above), each may correspond to a different protein domain or, in the case of polyprotein precursors, to a different mature protein.

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

reference

DOI no: 10.1016/S0969-2126(98)00037-9

Structure 6:351-361 (1998)

PubMed id: 9551556

Structural adaptations of the cold-active citrate synthase from an Antarctic bacterium.

R.J.Russell, U.Gerike, M.J.Danson, D.W.Hough, G.L.Taylor.

ABSTRACT

BACKGROUND: The structural basis of adaptation of enzymes to low temperature is poorly understood. Dimeric citrate synthase has been used as a model enzyme to study the structural basis of thermostability, the structure of the enzyme from organisms living in habitats at 55 degrees C and 100 degrees C having previously been determined. Here the study is extended to include a citrate synthase from an Antarctic bacterium, allowing us to explore the structural basis of cold activity and thermostability across the whole temperature range over which life is known to exit. RESULTS: We report here the first crystal structure of a cold-active enzyme, citrate synthase, isolated from an Antarctic bacterium, at a resolution of 2.09 A. In comparison with the same enzyme from a hyperthermophilic host, the cold-active enzyme has a much more accessible active site, an unusual electrostatic potential distribution and an increased relative flexibility of the small domain compared to the large domain. Several other features of the cold-active enzyme were also identified: reduced subunit interface interactions with no intersubunit ion-pair networks; loops of increased length carrying more charge and fewer proline residues; an increase in solvent-exposed hydrophobic residues; and an increase in intramolecular ion pairs. CONCLUSIONS: Enzymes from organisms living at the temperature extremes of life need to avoid hot or cold denaturation yet maintain sufficient structural integrity to allow catalytic efficiency. For hyperthermophiles, thermal denaturation of the citrate synthase dimer appears to be resisted by complex networks of ion pairs at the dimer interface, a feature common to other hyperthermophilic proteins. For the cold-active citrate synthase, cold denaturation appears to be resisted by an increase in intramolecular ion pairs compared to the hyperthermophilic enzyme. Catalytic efficiency of the cold-active enzyme appears to be achieved by a more accessible active site and by an increase in the relative flexibility of the small domain compared to the large domain.

Selected figure(s)

Figure 3.

The above figure is reprinted by permission from Cell Press: Structure (1998, 6, 351-361) copyright 1998.

Figure was selected by an automated process.