Identification of the leucine-rich amelogenin peptide (LRAP) as the translation product of an alternatively spliced transcript.

The polymerase chain reaction was used to amplify bovine tooth amelogenin cDNA, resulting in several products which were separated by agarose gel electrophoresis. Sequence determination of one of the products revealed that it encoded an amino acid sequence identical to that of a small leucine-rich amelogenin polypeptide (LRAP) previously characterized by protein sequencing. Comparison of the nucleotide sequence of this cDNA with that determined for the cloned bovine amelogenine gene strongly suggested that the LRAP transcript resulted from alternative splicing of the primary transcript of this gene, thus explaining the origin of the puzzling LRAP sequence. Analysis of the structure of LRAP suggests that the polypeptide might exhibit interesting properties relative to hydroxy apatite crystal formation.