Urea Unfolding Study of E. coli Alanyl-tRNA Synthetase and Its Monomeric Variants Proves the Role of C-Terminal Domain in Stability

Table 2

Thermodynamic parameters as obtained by fitting the far-UV CD data of WT-alaRS and its variants. The data was fitted in two-state (equation (1)) and three-state equation (equation (2)) for monomeric variants and WT-alaRS, respectively, using the software KyPlot (version 2.0 beta 15 (32 bits), Koichi Yoshioka, 1997–2001). The spectra were recorded in a 1 mm path length cuvette and within a region of 210–260 nm keeping the speed of the scan at 50 nm/min. For averaging, data from five independent scans were taken.

CD	(Kcal/mol)	(Kcal/mol)	(Kcal/mol/M)	(Kcal/mol/M)
WT	3.2 ± 0.1	13.9 ± 0.1	0.7 ± 0.1	1.7 ± 0.1
G674D	2.7 ± 0.2	—	0.7 ± 0.2	—
N700	2.6 ± 0.3	—	0.6 ± 0.2	—
N461	4.38 ± 0.3	—	0.8 ± 0.1	—

Values are the means of at least three independent experiments with standard errors indicated.