COMPARATIVE BIOCHEMISTRY OF ORGANIC MATRIX OF DEVELOPING ENAMEL .2. ULTRACENTRIFUGAL AND ELECTROPHORETIC CHARACTERIZATION OF PROTEINS SOLUBLE AT NEUTRAL PH

At a pH of 7.7 the neutral soluble proteins of both embryonic ovine and equine enamel have a concentration-dependent trinodal sedimentation boundary very similar to that previously found for the embryonic bovine enamel proteins. In the latter case, the 1 S node was primarily due to a number of chemically unique subunits, the 2 S node to intermediate(s), and the 12 S node to various high molecular weight aggregates, some of which are labile and in a state of (partial) equilibrium with the subunits during centrifugation, and others that are stable to dilution. When dissolved in 6 M urea, the sedimentation velocity patterns of the ovine and equine proteins are similar to that of the bovine enamel proteins: they show but one peak with an apparent sedimentation coefficient of about 1 S. The polyacrylamide gel electrophoresis patterns for these three proteins in 6 M urea are likewise similar: each shows approximately twenty bands, which, with a few exceptions, have a band-to-band correspondence. It was concluded that the physico-chemical data add further evidence that the neutral soluble proteins of developing enamel constitute a distinct class of structural proteins. © 1969.