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Volume 1 (2005), Issue 6, Pages 365-373
Research Article

New experimental approaches for investigating interactions between Pyrococcus furiosus carbamate kinase and carbamoyltransferases, enzymes involved in the channeling of thermolabile carbamoyl phosphate

Laboratorium voor Erfelijkheidsleer en Microbiologie, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium

Received 19 January 2005; Accepted 30 March 2005

Copyright © 2005 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A somewhat neglected but essential aspect of the molecular physiology of hyperthermophiles is the protection of thermolabile metabolites and coenzymes. An example is carbamoyl phosphate (CP), a precursor of pyrimidines and arginine, which is an extremely labile and potentially toxic intermediate. The first evidence for a biologically significant interaction between carbamate kinase (CK) and ornithine carbamoyltransferase (OTC) from Pyrococcus furiosus was provided by affinity electrophoresis and co-immunoprecipitation in combination with cross-linking (Massant et al. 2002). Using the yeast two-hybrid system, Hummel-Dreyer chromatography and isothermal titration calorimetry, we obtained additional concrete evidence for an interaction between CK and OTC, the first evidence for an interaction between CK and aspartate carbamoyltransferase (ATC) and an estimate of the binding constant between CK and ATC. The physical interaction between CK and OTC or ATC may prevent thermodenaturation of CP in the aqueous cytoplasmic environment. Here we emphasize the importance of developing experimental approaches to investigate the mechanism of thermal protection of metabolic intermediates by metabolic channeling and the molecular basis of transient protein–protein interactions in the physiology of hyperthermophiles.