Mass-spectrographic analysis of a porcine amelogenin identifies a single phosphorylated locus.
The amelogenins of the extracellular matrix of developing dental enamel, comprise a family of tissue-specific proteins which are postulated to play a central role in the biomineralization of dental enamel [1]. The primary structures of amelogenins derived from cow, pig, human, mouse and rat have now been elucidated by the interpretation of cDNA sequences or by direct amino acid sequence determinations [2-6] demonstrating a high degree of sequence homology between species [1]. However, the nature of post-translational modification of these proteins is less clear. In particular, early reports of amelogenin phosphorylation [7-8] have proved to be difficult to confirm by direct chemical analyses [1]. Using mass spectrographic analysis, we recently [9], reported that the lower molecular weight (5-7 kDa) bovine and porcine amelogenin polypeptides (TRAP and LRAP) contained a single phospho-serine residue at position 16Ser and, since these polypeptides are derived by proteolytic processing from the higher molecular weight "parent" amelogenins (18-25 kDa), we concluded that these precursor molecules must also be phosphorylated, as has previously been suggested [10]. In contrast to these observations, an extensive amino acid sequencing study of porcine amelogenins has recently reported no evidence for such phosphorylation [1]. We now report that a new analysis of the major porcine ("20K") amelogenin provides positive evidence for porcine amelogenin phosphorylation.
Fincham
A G
AG
Center for Craniofacial Molecular Biology, University of Southern California, School of Dentistry, Los Angeles 90033.
Moradian-Oldak
J
J
Sarte
P E
PE
D053523:Amelogenin; D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003743:Dental Enamel / Q000254:growth & development / Q000378:metabolism*; D003746:Dental Enamel Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D013058:Mass Spectrometry; D008963:Molar; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010766:Phosphorylation; D013552:Swine
D053523:Amelogenin; C507200:Amelx protein, mouse; C507201:Amelx protein, rat; D003746:Dental Enamel Proteins