1w0m: Difference between revisions

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 degrees C. The structure was determined, from both a hexagonal and an orthorhombic crystal form to resolutions of, 2.5A and 2.3A, 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, (betaalpha)(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 degrees C to 100 degrees 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.

1W0M is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Thermoproteus_tenax Thermoproteus tenax] with PO4 as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Triose-phosphate_isomerase Triose-phosphate isomerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.3.1.1 5.3.1.1] Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1W0M OCA].  

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