Light scattering studies of the effect of Ca2+ on the structure of porcine submaxillary mucin.
The effects of calcium ions on the solution properties of porcine submaxillary mucin (PSM) have been investigated by static and dynamic light scattering. The weight average molecular weights of PSM fractions are unaffected by the addition of up to 0.5M CaCl2: these data are within experimental error of those for solutions in 0.1M NaCl. The distribution of relaxation frequencies derived from the dynamic data shows the existence of two distinct relaxation modes. The average relaxation times have been interpreted to yield the z-average translational diffusion coefficient and the longest intramolecular relaxation time tau1. A plot of tau1 vs the mean value of 1/Rh-3z is linear, and consistent with plots of such data recorded for PSM in 0.1m NaCl and 6M GdnHCl solutions. However, the tau values and the associated results for the mean value of R-1h-1z in 0.5M CaCl2 are smaller than those determined in 0.1M NaCl. This suggests that the conformation of PSM in CaCl2 solution is more contracted than those in the other two solvents. These results are consistent with the compact packaging of mucin in the secretary granules that have elevated Ca2+ levels.
Varma
B K
BK
Department of Macromolecular Science, Case Western Reserve University, Cleveland, Ohio 44106.
Demers
A
A
Jamieson
A M
AM
Blackwell
J
J
Jentoft
N
N
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008027:Light; D008970:Molecular Weight; D009077:Mucins; D011487:Protein Conformation; D012542:Scattering, Radiation; D013363:Submandibular Gland / Q000032:analysis*; D013552:Swine; D013816:Thermodynamics
D009077:Mucins; D002118:Calcium