1PG5

CRYSTAL STRUCTURE OF THE UNLIGATED (T-STATE) ASPARTATE TRANSCARBAMOYLASE FROM THE EXTREMELY THERMOPHILIC ARCHAEON SULFOLOBUS ACIDOCALDARIUS

Summary for 1PG5

• Entry DOI: 10.2210/pdb1pg5/pdb
• Related: 8AT1
• Descriptor: Aspartate carbamoyltransferase, Aspartate carbamoyltransferase regulatory chain, ZINC ION, ... (4 entities in total)
• Functional Keywords: transferase
• Biological source: Sulfolobus acidocaldarius; More
• Total number of polymer chains: 2
• Total formula weight: 53111.87

Authors

De Vos, D.,Van Petegem, F.,Remaut, H.,Legrain, C.,Glansdorff, N.,Van Beeumen, J.J. (deposition date: 2003-05-27, release date: 2004-06-08, Last modification date: 2023-08-16)

Primary citation

De Vos, D.,Van Petegem, F.,Remaut, H.,Legrain, C.,Glansdorff, N.,Van Beeumen, J.J.
Crystal Structure of T State Aspartate Carbamoyltransferase of the Hyperthermophilic Archaeon Sulfolobus acidocaldarius.
J.Mol.Biol., 339:887-900, 2004

PubMed Abstract: 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.

PubMed: 15165857
DOI: 10.1016/j.jmb.2004.03.079

Experimental method

X-RAY DIFFRACTION (2.6 Å)