Hori T, Moriyama H, Kawaguchi J, Hayashi-Iwasaki Y, Oshima T, Tanaka N. The initial step of the thermal unfolding of 3-isopropylmalate dehydrogenase detected by the temperature-jump Laue method.
PROTEIN ENGINEERING 2000;
13:527-33. [PMID:
10964981 DOI:
10.1093/protein/13.8.527]
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Abstract
A temperature-jump (T-jump) time-resolved X-ray crystallographic technique using the Laue method was developed to detect small, localized structural changes of proteins in crystals exposed to a temperature increase induced by laser irradiation. In a chimeric protein between thermophilic and mesophilic 3-isopropylmalate dehydrogenases (2T2M6T), the initial structural change upon T-jump to a denaturing temperature (approximately 90 degrees C) was found to be localized at a region which includes a beta-turn and a loop located between the two domains of the enzyme. A mutant, 2T2M6T-E110P/S111G/S113E, having amino acid replacements in this beta-turn region with the corresponding residues of the thermophilic enzyme, showed greater stability than the original chimera (increase of T:(m) by approximately 10 degrees C) and no T-jump-induced structural change in this region was detected by our method. These results indicate that thermal unfolding of the original chimeric enzyme, 2T2M6T, is triggered in this beta-turn region.
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