Thermodynamics of replacing an α-helical Pro residue in the P40S mutant of Escherichia coli thioredoxin

被引:0
作者
Chakrabarti, A
Srivastava, S
Swaminathan, CP
Surolia, A
Varadarajan, R [1 ]
机构
[1] Indian Inst Sci, Mol Biophys Unit, Bangalore 560012, Karnataka, India
[2] Jawaharlal Ctr Adv Sci Res, Chem Biol Unit, Bangalore 560064, Karnataka, India
关键词
proline mutant; stability; thioredoxin;
D O I
暂无
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Escherichia coli thioredoxin is a 108 amino acid oxidoreductase and contains a single Met residue at position 37. The protein contains a long alpha-helical stretch between residues 32 and 49. The central residue of this helix, Pro40, has been replaced by Ser. The stabilities of the oxidized states of two proteins, the single mutant M37L and the double mutant M37L,P40S, have been characterized by differential scanning calorimetry (DSC) and also by a series of isothermal guanidine hydrochloride (GuHCl) melts in the temperature range of 277 to 333 K. The P40S mutation was found to stabilize the protein at all temperatures upto 340 K though both proteins had similar T-m values of about 356 K. At 298 K, the M37L,P40S mutant was found to be more stable than M37L by 1.5 kcal/mol. A combined analysis of GuHCl and calorimetric data was carried out to determine the enthalpy. entropy, and heat capacity change upon unfolding. At 298 K there was a large, stabilizing enthalpic effect in P40S though significant enthalpy-entropy compensation was observed and the two proteins had similar values of Delta C-p. Thus, replacement of a Pro in the interior of an alpha helix can have substantial effects on protein stability.
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页码:2455 / 2459
页数:5
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