RESUMO
The abundant hydrophobic, proline-glutamine, and histidine-rich (over 90%) amelogenins constitute the major class of proteins in forming extracellular enamel matrix. These are thought to play a major role in the structural organization and mineralization of developing enamel. The present report describes the successful sequencing of the major human amelogenin protein, by use of both Edman degradation and cDNA sequencing. When Edman degradation was used, over 75% of the primary structure of the protein was determined. This sequence was supplemented with cDNA sequencing studies, which revealed the predicted sequence of this protein. Together, they provide the complete sequence of an important human enamel protein. The information complements recent studies on bovine and human amelogenin genes. A comparison between the present results and the protein sequences predicted from the corresponding human amelogenin genomic coding regions and that of cDNA sequences of other species is described.
Assuntos
Proteínas do Esmalte Dentário/química , Proteínas do Esmalte Dentário/genética , Germe de Dente/química , Amelogenina , Sequência de Aminoácidos , Animais , Autoanálise/métodos , Sequência de Bases , Bovinos , Cromatografia Líquida de Alta Pressão , Quimotripsina/metabolismo , Brometo de Cianogênio/metabolismo , Proteínas do Esmalte Dentário/isolamento & purificação , Eletroforese em Gel de Poliacrilamida , Proteínas da Matriz Extracelular/química , Humanos , Camundongos , Dados de Sequência Molecular , Estrutura Molecular , Peso Molecular , Filogenia , Alinhamento de Sequência , Análise de Sequência de DNA/métodos , Especificidade da Espécie , Germe de Dente/ultraestruturaRESUMO
Transmission electron microscope observations on porcine enamel and secretory ameloblasts showed that silver methenamine material was located inside secretory vesicles in secretory ameloblasts and along the enamel crystals inside immature enamel. It is concluded that silver methenamine is able to stain enamel proteins selectively inside these tissues.
Assuntos
Ameloblastos/ultraestrutura , Amelogênese , Esmalte Dentário/ultraestrutura , Ameloblastos/química , Ameloblastos/citologia , Animais , Citratos , Ácido Cítrico , Cristalografia , Grânulos Citoplasmáticos/ultraestrutura , Esmalte Dentário/química , Metenamina/química , Microscopia Eletrônica , Compostos Organometálicos , Coloração e Rotulagem , Suínos , Porco Miniatura , Germe de Dente/ultraestrutura , UrânioRESUMO
A combined HCl-collagenase digestion technique and scanning electron microscopy were used to isolate the enamel organ and to confirm the presence of maturation ameloblasts of both ruffle-ended (RA) and smooth-ended (SA) types on maturing enamel in kitten permanent tooth germs. EDTA perfusion of animals fixed with aldehyde produced two or three belt-like shallow grooves (from 30 to 100 micron wide) running horizontally through the maturing enamel surface, coinciding closely with the SA distribution pattern. In animals that had been perfusion-fixed with unbuffered osmium tetroxide containing 2.5% potassium pyroantimonate, SEM-EDX analysis detected K in a superficial enamel layer overlaid by the SA layer. Potassium concentration decreased gradually toward the deeper layers. Very little K penetrated the enamel under the RA layer. Energy-dispersive x-ray analysis of Ca and P concentrations in the enamel revealed an even distribution of these elements throughout the superficial layer of maturing enamel. These results suggest that the SA layer forms an access route for K and EDTA and that, in spite of the obvious morphological and functional differences between RA and SA, the maturing enamel surfaces overlaid by these two cell types show similar degrees of mineralization.