MOLECULAR-WEIGHT DETERMINATION OF PHOSPHOLAMBAN OLIGOMER IN THE PRESENCE OF SODIUM DODECYL-SULFATE - APPLICATION OF LOW-ANGLE LASER-LIGHT SCATTERING PHOTOMETRY

The number of polypeptides constituting the oligomeric structure of canine phospholamban (a putative regulator of Ca2+-ATPase of cardiac sarcoplasmic reticulum) stable even in the presence of sodium dodecyl sulfate was estimated through determination of the molecular weight of the oligomer. Owing to the small molecular size, the low UV-absorptivity and the limited availability, the molecular weight determination required very sophisticated application of the following technique, used as the only recourse: low-angle laser light scattering measurement combined with high-performance gel chromatography. The molecular weight of phospholamban oligomer was found to be 30,400 and the number of subunits was concluded to be five after correction for the dependence of the apparent molecular weights on the protein concentration.