45Ca-Labeled Proteins Found in Porcine Developing Dental Enamel At an Early Stage of Development

Abstract

The existence of proteins having an affinity for calcium ions in immature enamel was searched for by autoradiography with ⁴⁵Ca used on the proteins transblotted from the gel to the membrane after electrophoresis. Mainly, two ⁴⁵Ca-labeled proteins (Mr = 27,000 and 29,000) were found in immature enamel at an early stage of development. Since these labeled proteins corresponded to the bands which were stained blue with Stains-all dye at the same molecular-weight positions, these proteins were always monitored by staining with Stains-all dye during the progressive purification process. The 27-kDa and 29-kDa proteins were partially purified by Sephadex G-100 gel filtration and DE cellulofine AH ion exchange chromatography. The amino acid compositions of both proteins were similar to each other, being relatively rich in Asp, Thr, Glu, and Ala, and different from those of amelogenins and enamelins. These two proteins do not appear to be contaminants from the cells during preparation, based on the result of comparison of the proteins extracted from the cellular layers of enamel organ with those of immature enamel.