Structure of a GTP-dependent Bacterial PEP-carboxykinase from Corynebacterium glutamicum

• Published in: The international journal of biochemistry & cell biology Vol. 40; no. 8; pp. 1597 - 1603
• Main Authors: Aich, Sanjukta, Prasad, Lata, Delbaere, Louis T.J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01.01.2008
• Subjects: Corynebacterium glutamicum; Corynebacterium glutamicum - enzymology; Crystallography, X-Ray; GTP-dependent PCK; Models, Molecular; P-loop conformation; Phosphoenolpyruvate Carboxykinase (GTP) - chemistry; Protein Conformation; Protein Structure, Quaternary; Spectrometry, Fluorescence; GTP-dependent PCK; Corynebacterium glutamicum; P-loop conformation
• ISSN: 1357-2725; 1878-5875
• DOI: 10.1016/j.biocel.2007.12.002

GTP-dependent phosphoenolpyruvate carboxykinase (PCK) is the key enzyme that controls the blood glucose level during fasting in higher animals. Here we report the first substrate-free structure of a GTP-dependent phosphoenolpyruvate (PEP) carboxykinase from a bacterium, Corynebacterium glutamicum (CgPCK). The protein crystallizes in space group P2 1 with four molecules per asymmetric unit. The 2.3 Å resolution structure was solved by molecular replacement using the human cytosolic PCK (hcPCK) structure (PDB ID: 1KHF) as the starting model. The four molecules in the asymmetric unit pack as two dimers, and is an artifact of crystal packing. However, the P-loop and the guanine binding loop of the substrate-free CgPCK structure have different conformations from the other published GTP-specific PCK structures, which all have bound substrates and/or metal ions. It appears that a change in the P-loop and guanine binding loop conformation is necessary for substrate binding in GTP-specific PCKs, as opposed to overall domain movement in ATP-specific PCKs.