title: Type I collagen-phosphophoryn interactions: specificity of the monomer-monomer binding.
abstract: It has been postulated that phosphophoryn (PP) molecules bind specifically to type I collagen fibrils as the key event in inducing matrix mineralization in dentin. The nature and specificity of the collagen molecule-PP interaction has been examined by rotary shadowing-electron microscopy of mixtures of native, monomeric lathyritic rat skin collagen and purified rat incisor PP. An antibody to the amino-telopeptide of the collagen alpha1(I)-chain was used to determine the N-terminal end of the collagen molecules. Solutions of collagen and PP in 0.01 M ammonium formate (+/- antibody) were mixed and spread in 70% glycerol-30% 0.01 M ammonium formate on freshly cleaved mica surfaces using the sandwich technique. After rotary shadowing with Pt and backcoating with a carbon film, the spreads were viewed in a JEOL 1200EX TEM. The PP appeared as 15-nm diameter globules, the collagen as semi-flexible 270 nm filaments. At neutral pH and low PP/collagen mixing ratios, a single interaction site was evident, centered at approximately 210 nm from the N-terminus. The binding interaction induced a local conformational change in the collagen, bending the molecule and reducing its effective length. The sequence within the collagen-PP-binding domain has a net-positive charge but contains both positively and negatively charged groups.
authors.affiliation: Department of Basic and Behavioral Sciences, Division of Oral Biology, Northwestern University, 303 E. Chicago Ave., Chicago, Illinois, 60611, USA.
authors.forename: T
authors.initials: T
authors.lastname: Dahl
authors.forename: B
authors.initials: B
authors.lastname: Sabsay
authors.forename: A
authors.initials: A
authors.lastname: Veis
mesh_terms: D000595:Amino Acid Sequence; D000629:Aminopropionitrile / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D003094:Collagen / Q000648:ultrastructure*; D003804:Dentin / Q000737:chemistry; D007180:Incisor / Q000737:chemistry; D007842:Lathyrism / Q000139:chemically induced; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D010316:Particle Size; D010750:Phosphoproteins / Q000648:ultrastructure*; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000737:chemistry
chemical_list: D010750:Phosphoproteins; C017630:phosphophoryn; C027243:beta-aminopropionitrile fumarate; D000629:Aminopropionitrile; D003094:Collagen