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KMID : 0364820140500040275
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Korean Journal of Microbiology
2014 Volume.50 No. 4 p.275 ~ p.280
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Fluorescence Characteristics of a Tryptophan Mutant of Leucine-responsive Regulatory Protein (Lrp)
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Robert Pokoo
Lee Eui-Ho
Lee Chan-Yong
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Abstract
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Leucine-responsive Regulatory Protein (Lrp) from Escherichia coli is an 18.8 kDa protein composed of 164 amino acids. Wild type Lrp (Lrp Wt) does not possess any tryptophan amino acid which has strong intrinsic fluorescence, whereas the mutant Lrp R145W contains a single tryptophan at the position 145 in the leucine-responsive domain. To investigate the fluorescence character, the Lrp R145W and Lrp Wt proteins were purified. The fluorescence intensity of Lrp R145W is much higher than that of wild type protein, and the intensity of Lrp R145W was decreased by binding to its specific DNA designed from ilvIH operon and to L-leucine. In addition, the tryptophan fluorescence intensity of Lrp R145W was strongly quenched by addition of acrylamide even in the least amount of concentration as well as by urea. The data obtained from this study may give valuable information on the three dimensional structure of Lrp R145W.
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KEYWORD
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fluorescence, global regulatory protein (Lrp), leucine
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