CD spectra analysis. CD spectra demonstrate that the R1165C and E1841K mutations decrease the coiled-coil structure of the tail. Spectra from 240 nm to 200 nm (x-axis) were taken for all samples and were plotted versus their mean residue ellipticity (degrees cm2 dmole–1) (y-axis). All show the characteristic pattern (minima at 222 nm and 208 nm) for helical proteins, but not all show the characteristic pattern for coiled-coil proteins (222 nm minima is greater than 208 nm minima). The wild-type tail fragment (panel Ai) showed a spectrum very typical of coiled-coil proteins as did R1933Stop (Ci) and D1424N (Ei). Two mutations R1165C (Bi) and E1841K (Di) have altered CD spectra (208 nm is greater than 222 nm) indicating a partial loss of coiled-coil structure. Overlays of each mutant (dark circles) compared with wild type are also shown: WT versus R1165C (Bii), WT versus R1933Stop (Cii), WT versus E1841K (Dii), and WT versus R1933Stop (Eii). The ratios of molar ellipticity at 222 nm to 208 were calculated and tabulated. For completeness and accuracy, only CD spectra data points with a dynode voltage lower than 600 V are shown.
