Studies of the heterogeneity of human pituitary LH by fast protein liquid chromatography

The Pharmacia fast protein liquid chromatography system was employed to fractionate a purified preparation of human LH (hLH) on the anion exchanger Mono Q at pH 7 X 8 into 14 sub-fractions. Each of the sub-fractions was characterized by its behaviour on polyacrylamide gel electrophoresis, sodium dodecyl sulphate (SDS) gel electrophoresis, LH receptor binding activity and sialic acid content. All sub-fractions contained sialic acid, were active in binding to LH receptors, and exhibited components typical of hLH subunits on SDS gel electrophoresis. None of the subfractions was homogeneous with respect to charge. There is evidence that part of the heterogeneity results from the presence in some molecules of an internal proteolytic cleavage within the beta-subunit, and fractions enriched in species containing such cleavages were prepared by this method.