Amelogenin self-assembly and the role of the proline located within the carboxyl-teleopeptide.
A hallmark of biological systems is a reliance on protein assemblies to perform complex functions. We have focused attention on mammalian enamel formation because it relies on a self-assembling protein complex to direct mineral habit. The principle protein of enamel is amelogenin that self-assembles to form nanospheres. In mice, the principal amelogenin product is a 180 amino acid hydrophobic protein. The yeast two-hybrid assay has been used to demonstrate the importance of amelogenin self-assembly domains. We have generated specific variants of amelogenin to analyze contributions of individual amino acids to the self-assembly process. These amelogenin variants have been produced either by deleting carboxyl-terminal amino acids (to generate proteins that relate to the documented proteolytic products of mouse amelogenin) or by a site-directed mutagenesis approach. Assessment of variant amelogenins truncated at the carboxyl-terminal imply that the proline at position 169 of mouse amelogenin (M180) plays a significant role in amelogenin self-assembly. Site-directed mutagenesis of this particular proline, however, failed to disrupt the amelogenin self-assembly property. These conflicting data add to the complexity of protein-protein assembly mechanisms as they relate to the enamel matrix. Available data suggest a robustness of this enamel protein (amelogenin) that ensures a functional, even though mechanically less than optimal, enamel results despite either minor or major genetic errors to the amelogenin gene locus.
Paine
Michael L
ML
University of Southern California, School of Dentistry, Center for Craniofacial Molecular Biology, Los Angeles, California 90033, USA. paine@hsc.usc.edu
Wang
Hong-Jun
HJ
Snead
Malcolm L
ML
D000566:Amelogenesis / Q000502:physiology*; D053523:Amelogenin; D000818:Animals; D002113:Calcification, Physiologic; D017931:DNA Primers / Q000737:chemistry; D003746:Dental Enamel Proteins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry; D011392:Proline / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D020798:Two-Hybrid System Techniques; D001616:beta-Galactosidase / Q000378:metabolism
D053523:Amelogenin; C507200:Amelx protein, mouse; D017931:DNA Primers; D003746:Dental Enamel Proteins; D010446:Peptide Fragments; D011392:Proline; D001616:beta-Galactosidase