Fig. 4.
Calcium effect on PEVK structure. (A) Fluorescence emission spectrum of wt126-133. Numbers indicate [Ca2+] in pCa. Intensity increases with [Ca2+] between pCa 9 and 4 and then saturates (curves at pCa 4 and 3 exactly overlap). Two bottom curves (green and black) also overlap: they were in 0 mM (green) and 4 mM (black) magnesium. (B Upper) Calcium-dependent fluorescence (FL) intensity change at λmax. (Mean values ± SEM of three experiments.) Also shown are PL values (PLL) of wt119-136 (filled symbols) and wt126-133 (open circles). (Each data point is the mean of >100 force curves obtained from six experiments.) (Lower) Calcium dependence of ultrasonic velocity of solutions containing wt126-133 (PEVK repeats and E-rich exon) and wt121-128 (PEVK repeats only). Change in velocity is shown relative to the maximal change observed for wt126-133 between pCa 8.5 and 5.0 (velocity change of -16.7 cm/s). Note a steep and significant decrease in velocity only for wt126-133.