title: Ameloblastin peptide encoded by exon 5 interacts with amelogenin N-terminus.
abstract: Interactions between enamel matrix proteins are important for enamel biomineralization. In recentin situstudies, we showed that the N-terminal proteolytic product of ameloblastin co-localized with amelogenin around the prism boundaries. However, the molecular mechanisms of such interactions are still unclear. Here, in order to determine the interacting domains between amelogenin and ameloblastin, we designed four ameloblastin peptides derived from different regions of the full-length protein (AB1, AB2 and AB3 at N-terminus, and AB6 at C-terminus) and studied their interactions with recombinant amelogenin (rP172), and the tyrosine-rich amelogenin polypeptide (TRAP). A series of amelogenin Trp variants (rP172(W25), rP172(W45) and rP172(W161)) were also used for intrinsic fluorescence spectroscopy. Fluorescence spectra of rP172 titrated with AB3, a peptide encoded by exon 5 of ameloblastin, showed a shift in λmaxin a dose-dependent manner, indicating molecular interactions in the region encoded by exon 5 of ameloblastin. Circular dichroism (CD) spectra of amelogenin titrated with AB3 showed that amelogenin was responsible for forming α-helix in the presence of ameloblastin. Fluorescence spectra of amelogenin Trp variants as well as the spectra of TRAP titrated with AB3 showed that the N-terminus of amelogenin is involved in the interaction between ameloblastin and amelogenin. We suggest that macromolecular co-assembly between amelogenin and ameloblastin may play important roles in enamel biomineralization.
authors.affiliation: Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, CA.
authors.forename: Jingtan
authors.initials: J
authors.lastname: Su
authors.affiliation: Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, CA.
authors.forename: Karthik Balakrishna
authors.initials: KB
authors.lastname: Chandrababu
authors.affiliation: Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, CA.
authors.forename: Janet
authors.initials: J
authors.lastname: Moradian-Oldak
keywords: ameloblastin; amelogenin; enamel; matrix protein; protein-protein interaction