Structure and function of a regulated archaeal triosephosphate isomerase adapted to high temperature

Walden, H. , Taylor, G. L., Lorentzen, E., Pohl, E., Lilie, H., Schramm, A., Knura, T., Stubbe, K., Tjaden, B. and Hensel, R. (2004) Structure and function of a regulated archaeal triosephosphate isomerase adapted to high temperature. Journal of Molecular Biology, 342(3), pp. 861-875. (doi: 10.1016/j.jmb.2004.07.067) (PMID:15342242)

Abstract

Triosephophate isomerase (TIM) is a dimeric enzyme in eucarya, bacteria and mesophilic archaea. In hyperthermophilic archaea, however, TIM exists as a tetramer composed of monomers that are about 10% shorter than other eucaryal and bacterial TIM monomers. We report here the crystal structure of TIM from Thermoproteus tenax, a hyperthermophilic archaeon that has an optimum growth temperature of 86 °C. The structure was determined from both a hexagonal and an orthorhombic crystal form to resolutions of 2.5 Å and 2.3 Å, and refined to R-factors of 19.7% and 21.5%, respectively. In both crystal forms, T. tenax TIM exists as a tetramer of the familiar (βα)8-barrel. In solution, however, and unlike other hyperthermophilic TIMs, the T. tenax enzyme exhibits an equilibrium between inactive dimers and active tetramers, which is shifted to the tetramer state through a specific interaction with glycerol-1-phosphate dehydrogenase of T. tenax. This observation is interpreted in physiological terms as a need to reduce the build-up of thermolabile metabolic intermediates that would be susceptible to destruction by heat. A detailed structural comparison with TIMs from organisms with growth optima ranging from 15 °C to 100 °C emphasizes the importance in hyperthermophilic proteins of the specific location of ionic interactions for thermal stability rather than their numbers, and shows a clear correlation between the reduction of heat-labile, surface-exposed Asn and Gln residues with thermoadaptation. The comparison confirms the increase in charged surface-exposed residues at the expense of polar residues.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Walden, Professor Helen
• Authors: Walden, H., Taylor, G. L., Lorentzen, E., Pohl, E., Lilie, H., Schramm, A., Knura, T., Stubbe, K., Tjaden, B., and Hensel, R.
• College/School: College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
• Journal Name: Journal of Molecular Biology
• Publisher: Elsevier
• ISSN: 0022-2836
• ISSN (Online): 1089-8638
• Published Online: 02 August 2004