8BPS

Aspartate transcarbamoylase mutant (N2045C, R2238C) from Chaetomium thermophilum CAD-like in apo form

Summary for 8BPS

• Entry DOI: 10.2210/pdb8bps/pdb
• Related: 8BPL
• Descriptor: Carbamoyl-phosphate synthase (glutamine-hydrolyzing), GLYCEROL (3 entities in total)
• Functional Keywords: nucleotide metabolism, de novo pyrimidine synthesis, cad, cysteine, disulfide bridge, protein stability, crosslinking, succinate, multienzymatic protein, transferase
• Biological source: Thermochaetoides thermophila
• Total number of polymer chains: 1
• Total formula weight: 36047.60

Authors

del Cano-Ochoa, F.,Ramon-Maiques, S. (deposition date: 2022-11-25, release date: 2023-02-01, Last modification date: 2024-10-23)

Primary citation

Del Cano-Ochoa, F.,Rubio-Del-Campo, A.,Ramon-Maiques, S.
A Tailored Strategy to Crosslink the Aspartate Transcarbamoylase Domain of the Multienzymatic Protein CAD.
Molecules, 28:-, 2023

PubMed Abstract: CAD is a 1.5 MDa hexameric protein with four enzymatic domains responsible for initiating de novo biosynthesis of pyrimidines nucleotides: glutaminase, carbamoyl phosphate synthetase, aspartate transcarbamoylase (ATC), and dihydroorotase. Despite its central metabolic role and implication in cancer and other diseases, our understanding of CAD is poor, and structural characterization has been frustrated by its large size and sensitivity to proteolytic cleavage. Recently, we succeeded in isolating intact CAD-like particles from the fungus with high yield and purity, but their study by cryo-electron microscopy is hampered by the dissociation of the complex during sample grid preparation. Here we devised a specific crosslinking strategy to enhance the stability of this mega-enzyme. Based on the structure of the isolated ATC domain, we inserted by site-directed mutagenesis two cysteines at specific locations that favored the formation of disulfide bridges and covalent oligomers. We further proved that this covalent linkage increases the stability of the ATC domain without damaging the structure or enzymatic activity. Thus, we propose that this cysteine crosslinking is a suitable strategy to strengthen the contacts between subunits in the CAD particle and facilitate its structural characterization.

PubMed: 36677714
DOI: 10.3390/molecules28020660

Experimental method

X-RAY DIFFRACTION (2.03 Å)