title: Tooth enamel protein amelogenin binds to ameloblast cell membrane-mimicking vesicles via its N-terminus.
abstract: We have recently reported that the extracellular enamel protein amelogenin has affinity to interact with phospholipids and proposed that such interactions may play key roles in enamel biomineralization as well as reported amelogenin signaling activities. Here, in order to identify the liposome-interacting domains of amelogenin we designed four different amelogenin mutants containing only a single tryptophan at positions 25, 45, 112 and 161. Circular dichroism studies of the mutants confirmed that they are structurally similar to the wild-type amelogenin. Utilizing the intrinsic fluorescence of single tryptophan residue and fluorescence resonance energy transfer [FRET], we analyzed the accessibility and strength of their binding with an ameloblast cell membrane-mimicking model membrane (ACML) and a negatively charged liposome used as a membrane model. We found that amelogenin has membrane-binding ability mainly via its N-terminal, close to residues W25 and W45. Significant blue shift was also observed in the fluorescence of a N-terminal peptide following addition of liposomes. We suggest that, among other mechanisms, enamel malformation in cases of Amelogenesis Imperfecta (AI) with mutations at the N-terminal may be the result of defective amelogenin-cell interactions.
authors.affiliation: Center for Craniofacial Molecular Biology, Division of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA.
authors.forename: Sowmya Bekshe
authors.initials: SB
authors.lastname: Lokappa
authors.affiliation: Center for Craniofacial Molecular Biology, Division of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA.
authors.forename: Karthik Balakrishna
authors.initials: KB
authors.lastname: Chandrababu
authors.affiliation: Center for Craniofacial Molecular Biology, Division of Biomedical Sciences, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA. Electronic address: joldak@usc.edu.
authors.forename: Janet
authors.initials: J
authors.lastname: Moradian-Oldak
mesh_terms: D000565:Ameloblasts / Q000166:cytology* / Q000378:metabolism; D000567:Amelogenesis Imperfecta / Q000235:genetics; D053523:Amelogenin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D031541:Fluorescence Resonance Energy Transfer; D006863:Hydrogen-Ion Concentration; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010715:Phosphatidylglycerols / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013552:Swine; D014364:Tryptophan / Q000737:chemistry
chemical_list: D053523:Amelogenin; D008081:Liposomes; D010715:Phosphatidylglycerols; C060037:1-palmitoyl-2-oleoylglycero-3-phosphoglycerol; D014364:Tryptophan
keywords: Ameloblasts; Amelogenin; Enamel; Intrinsic florescence spectroscopy; Liposomes