title: Amelogenin processing by MMP-20 prevents protein occlusion inside calcite crystals.
abstract: Calcite crystals were grown in the presence of full-length amelogenin and during its proteolysis by recombinant human matrix metalloproteinase 20 (rhMMP-20). Recombinant porcine amelogenin (rP172) altered the shape of calcite crystals by inhibiting the growth of steps on the {104} faces and became occluded inside the crystals. Upon co-addition of rhMMP-20, the majority of the protein was digested resulting in a truncated amelogenin lacking the C-terminal segment. In rP172-rhMMP-20 samples, the occlusion of amelogenin into the calcite crystals was drastically decreased. Truncated amelogenin (rP147) and the 25-residue C-terminal domain produced crystals with regular shape and less occluded organic material. Removal of the C-terminal diminished the affinity of amelogenin to the crystals and therefore prevented occlusion. We hypothesize that HAP and calcite interact with amelogenin in a similar manner. In the case of each material, full-length amelogenin binds most strongly, truncated amelogenin binds weakly and the C-terminus alone has the weakest interaction. Regarding enamel crystal growth, the prevention of occlusion into maturing enamel crystals might be a major benefit resulting from the selective cleavage of amelogenin at the C-terminus by MMP-20. Our data have important implications for understanding the hypomineralized enamel phenotype in cases of amelogenesis imperfecta resulting from MMP-20 mutations and will contribute to the design of enamel inspired biomaterials.
authors.affiliation: Center for Craniofacial Molecular Biology, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA.
authors.forename: Keith M
authors.initials: KM
authors.lastname: Bromley
authors.forename: Rajamani
authors.initials: R
authors.lastname: Lakshminarayanan
authors.forename: Mitchell
authors.initials: M
authors.lastname: Thompson
authors.forename: Sowmya B
authors.initials: SB
authors.lastname: Lokappa
authors.forename: Victoria A
authors.initials: VA
authors.lastname: Gallon
authors.forename: Kang R
authors.initials: KR
authors.lastname: Cho
authors.forename: S Roger
authors.initials: SR
authors.lastname: Qiu
authors.forename: Janet
authors.initials: J
authors.lastname: Moradian-Oldak