Relative molecular mass determination of a major, highest relative molecular mass extracellular amelogenin of developing bovine enamel

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Abstract
Proteins of developing bovine enamel were fractionated by molecular sieving and ion‐exchange chromatography. The major fraction corresponding to the highest M r amelogenin of M r ~26000–30000 was isolated and its M r determined by SDS‐PAGE, molecular sieving on G‐100 resin and high performance liquid chromatography and by sedimentation‐equilibrium ultracentrifugation, the latter three procedures in guanidine hydrochloride. SDS‐PAGE and HPLC molecular sieving, employing commonly used M r standards, gave M r values of ~22000–26000. SDS‐PAGE and HPLC molecular sieving, using proline‐rich CNBr peptides of collagen as standards, and sedimentation‐equilibrium ultracentrifugation, gave M r values of ~15000–18000 and ~17385, respectively. These latter values correspond well with those reported earlier and with the M r of the major amelogenin computed from recent amino acid sequence data (~19000). It is concluded that the recently described, highest M r amelogenin of M r = 26000–30000 is not a new component but is identical to the proline‐rich components having relative molecular masses ranging from 15000 to 18000 described much earlier by several groups of workers.