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KMID : 0613820020120040464
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Journal of Life Science
2002 Volume.12 No. 4 p.464 ~ p.468
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Effect of Substituted Residue 139 and 258 on Structural Changes of Mutant Tryptophan Synthase Pro96→Leu α-Subunit
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Lee Joo-Youn
Jeong Jae-Kap
Shin Hae-Ja
Lim Woon-Ki
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Abstract
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Enzymatic activities and fluorescence spectroscopic properties of the double mutant proteins P96L/F139W, P96L/F258W and a triple mutant protein P96L/F139W/F258W of tryptophan synthase α subunit from Escherichia coli was examined to study tertiary and local structure changes around the tryptophan residues. The enzymatic activities of P96L/F139W and P96L/F258W were similar, but P96L/F139W/F258W had lower activity, as compared to wild type. The fluorescence intensities of double mutant, P96L/F139W and P96L/F258W, were decreased but that of a triple mutant, P96L/F139W/F258W, was increased when compared to wild type. The sum of the maximum fluorescence intensity (fluorescence intensity at the λmax) for the double mutant proteins was not equal to the intensity seen in the triple mutant protein. The enzymatic activity and fluorescence data indicate that the replacement of Pro96→Leu might affect on the stability of helix 8 and the loop located between strand 4 and helix4. The result suggests that the tertiary structure of triple mutant (P96L/F139W/F258W), being different from wild type, might have more compact residual structure at the vicinity of 139 and 258
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KEYWORD
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Tryptophan synthase α subunit, mutant
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