Further studies on the binding of divalent cations to the phosphoglycoprotein phosvitin.
Dialysis equilibrium measurements at 25 degrees indicate that, at pH 6.8 and at a concentration of 1.0 times 10(-10) 3 M MnC12 or CoC12, phosvitin binds 113 Mn2+ and 120 Co2+. The binding is cooperative at low cation concentrations. The number of Mg2+, Ca2+, Mn2+, and Co2+ bound is not affected by temperatures of up to 60 degrees; however, the cooperactivity is enhanced. Optical rotatory dispersion and circular dichroism studies indicate that a conformational change occurs on binding of Mn2+ and Co2+ which parallels the one produced by Ca2+ and reported elsewhere [Grizzuti, K., and Perlmann, G.E. (1973), Biochemistry 12, 4399]. The conformational changes induced by Mg2+ and Mn2+ follow different paths. Upon binding of Mn2+ and Co2+ the intrinsic viscosity, [eta], of phosvitin decreases from about 0.5 to 0.03 dl/g, while Mg2+ and Ca2+ decrease [eta] to 0.048 dl/g. The ultraviolet absorption spectrum of phosvitin is altered upon binding of Ca2+, Mn2+, and Co2+, but not upon binding of Mg2+; an increase of the temperature to 60% has no further effect on the spectra.
D001665:Binding Sites; D002118:Calcium; D002413:Cations, Divalent; D002942:Circular Dichroism; D003035:Cobalt; D004527:Egg Proteins; D007700:Kinetics; D008274:Magnesium; D008345:Manganese; D009905:Optical Rotatory Dispersion; D010774:Phosvitin; D011485:Protein Binding; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
D002413:Cations, Divalent; D004527:Egg Proteins; D003035:Cobalt; D008345:Manganese; D010774:Phosvitin; D008274:Magnesium; D002118:Calcium