The electron microscopic localization of the neutral soluble proteins of developing bovine enamel

Abstract

Electron microscopy, coupled with amino acid analyses, has shown that the proline- and histidine-rich protein fractions of embryonic bovine enamel which are solubilized in cold, neutral buffer solutions, are derived primarily from the inter- and intraprismatic filaments. In contrast to the majority of the inter- and intraprismatic filament proteins, the prism sheath proteins were relatively insoluble in neutral buffer solutions. There were a small number of filaments in many of the prisms which were not solubilized after prolonged extraction with neutral buffer solution. Both these filaments and the prism sheaths were soluble in dilute acetic acid. There were significant differences in the compositions of the proteins of the inter- and intraprismatic filaments and those of the prism sheaths, which may reflect their different biological functions.