2btm
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(New page: 200px<br /><applet load="2btm" size="450" color="white" frame="true" align="right" spinBox="true" caption="2btm, resolution 2.4Å" /> '''DOES THE HIS12-LYS13 ...)
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Revision as of 06:47, 21 November 2007
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DOES THE HIS12-LYS13 PAIR PLAY A ROLE IN THE ADAPTATION OF THERMOPHILIC TIMS TO HIGH TEMPERATURES?
Overview
The thermophilic triose-phosphate isomerases (TIMs) of Bacillus, stearothermophilus (bTIM) and Thermotoga maritima (tTIM) have been found, to possess a His12-Lys13 pair instead of the Asn12-Gly13 pair normally, present in mesophilic TIMs. His12 in bTIM was proposed to prevent, deamidation at high temperature, while the precise role of Lys13 is, unknown. To investigate the role of the His12 and Lys13 pair in the, enzyme's thermoadaptation, we reintroduced the "mesophilic residues" Asn, and Gly into both thermophilic TIMs. Neither double mutant displayed, diminished structural stability, but the bTIM double mutant showed, drastically reduced catalytic activity. No similar behavior was observed, with the tTIM double mutant, suggesting that the presence of the His12 and, Lys13 cannot be systematically correlated to thermoadaptation in TIMs. We, determined the crystal structure of the bTIM double mutant complexed with, 2-phosphoglycolate to 2.4-A resolution. A molecular dynamics simulation, showed that upon substitution of Lys13 to Gly an increase of the, flexibility of loop 1 is observed, causing an incorrect orientation of the, catalytic Lys10. This suggests that Lys13 in bTIM plays a crucial role in, the functional adaptation of this enzyme to high temperature. Analysis of, bTIM single mutants supports this assumption.
About this Structure
2BTM is a Single protein structure of sequence from Geobacillus stearothermophilus with PGA as ligand. Active as Triose-phosphate isomerase, with EC number 5.3.1.1 Full crystallographic information is available from OCA.
Reference
Lys13 plays a crucial role in the functional adaptation of the thermophilic triose-phosphate isomerase from Bacillus stearothermophilus to high temperatures., Alvarez M, Wouters J, Maes D, Mainfroid V, Rentier-Delrue F, Wyns L, Depiereux E, Martial JA, J Biol Chem. 1999 Jul 2;274(27):19181-7. PMID:10383424
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