A LOW-ANGLE LASER-LIGHT SCATTERING STUDY OF THE ASSOCIATION BEHAVIOR OF A MAJOR MEMBRANE-PROTEIN OF RHODOSPIRILLUM-RUBRUM CHROMATOPHORE AT VARIOUS CONCENTRATIONS OF SODIUM DODECYL-SULFATE WHERE POLYPEPTIDES DERIVED FROM WATER-SOLUBLE GLOBULAR-PROTEINS ARE SOLUBILIZED MONOMERICALLY

The major membrane protein of the R. rubrum chromatophore was solubilized in the presence of free sodium dodecyl sulfate (SDS) concentrations > 0.8 mM. At this concentration, the protein was highly associated to give a weight-averaged MW as high as 1,000,000, as determined by the low-angle laser light scattering technique. With the increase of free SDS concentration, the aggregates were progressively dissociated to give a MW of 8300 at the critical micelle concentration of SDS. Three protein polypeptides derived from typical water-soluble globular proteins, bovine serum albumin, ovalbumin and .beta.-lactoglobulin, were solubilized monomerically even at 0.8 mM free SDS. Apparently, there is a substantial difference in the mode of solubilization between polypeptides derived from intrinsic membrane proteins and those from water-soluble globular proteins.