Flexibility of the Cytoplasmic Domain of the Phototaxis Transducer II from Natronomonas pharaonis
Figure 2
(a) Effect of
addition mono- and bivalent salts on far-UV CD spectra of pHtrII-cyt recorded
at protein concentration of 0.1 mg/mL at +20. Dotted line is the spectrum of
pHtrII-cyt in PBS, black spectrum corresponds to the addition of 4 M LiCl, red—4 M NaCl, green—4 M KCl, blue—4 M RbCl, cyan—4 M CsCl, magenta—4 M Ca, and yellow—4 M Mg. (b) Thermal denaturation
plots of pHtrII-cyt monitored at 222 nm in PBS and in PBS +
monovalent salts . Colors are the
same as in (a). (c) Thermal denaturation plots of pHtrII-cyt monitored at 222
nm in PBS , PBS + 90% glycerol , PBS + 98.5% TFE , and in PBS + 40% saturation
ammonium sulfate . The straight lines
represent sigmoidal fits of the experimental data. Dependences of the mean
residue molar ellipticity at 222 nm (d) and midpoints of thermal denaturation
monitored at 222 nm (e) of pHtrII-cyt in PBS + 4 M of the corresponding
chloride salt on the hydration radii of alkali cations used
in the study. The straight line in (e) represents linear fit with correlation
coefficient of 0.9. Note that the spectra in the presence of Mg or Ca were recorded in Tris buffer (buffer B, pH 7.2) instead of
PBS because of the low solubility of these salts in PBS.
