1PG5 image
Deposition Date 2003-05-27
Release Date 2004-06-08
Last Version Date 2023-08-16
Entry Detail
PDB ID:
1PG5
Keywords:
Title:
CRYSTAL STRUCTURE OF THE UNLIGATED (T-STATE) ASPARTATE TRANSCARBAMOYLASE FROM THE EXTREMELY THERMOPHILIC ARCHAEON SULFOLOBUS ACIDOCALDARIUS
Biological Source:
Source Organism:
Host Organism:
Method Details:
Experimental Method:
Resolution:
2.60 Å
R-Value Free:
0.23
R-Value Work:
0.19
R-Value Observed:
0.19
Space Group:
P 63 2 2
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:Aspartate carbamoyltransferase
Gene (Uniprot):pyrB
Chain IDs:A
Chain Length:299
Number of Molecules:1
Biological Source:Sulfolobus acidocaldarius
Polymer Type:polypeptide(L)
Molecule:Aspartate carbamoyltransferase regulatory chain
Gene (Uniprot):pyrI
Chain IDs:B
Chain Length:168
Number of Molecules:1
Biological Source:Sulfolobus acidocaldarius
Ligand Molecules
Primary Citation
Crystal Structure of T State Aspartate Carbamoyltransferase of the Hyperthermophilic Archaeon Sulfolobus acidocaldarius.
J.Mol.Biol. 339 887 900 (2004)
PMID: 15165857 DOI: 10.1016/j.jmb.2004.03.079

Abstact

Aspartate carbamoyltransferase (ATCase) is a model enzyme for understanding allosteric effects. The dodecameric complex exists in two main states (T and R) that differ substantially in their quaternary structure and their affinity for various ligands. Many hypotheses have resulted from the structure of the Escherichia coli ATCase, but so far other crystal structures to test these have been lacking. Here, we present the tertiary and quaternary structure of the T state ATCase of the hyperthermophilic archaeon Sulfolobus acidocaldarius (SaATC(T)), determined by X-ray crystallography to 2.6A resolution. The quaternary structure differs from the E.coli ATCase, by having altered interfaces between the catalytic (C) and regulatory (R) subunits, and the presence of a novel C1-R2 type interface. Conformational differences in the 240 s loop region of the C chain and the C-terminal region of the R chain affect intersubunit and interdomain interfaces implicated previously in the allosteric behavior of E.coli ATCase. The allosteric-zinc binding domain interface is strengthened at the expense of a weakened R1-C4 type interface. The increased hydrophobicity of the C1-R1 type interface may stabilize the quaternary structure. Catalytic trimers of the S.acidocaldarius ATCase are unstable due to a drastic weakening of the C1-C2 interface. The hyperthermophilic ATCase presents an interesting example of how an allosteric enzyme can adapt to higher temperatures. The structural rearrangement of this thermophilic ATCase may well promote its thermal stability at the expense of changes in the allosteric behavior.

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Primary Citation of related structures