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

摘要

>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.