Characteristics of phosphorylated and non-phosphorylated dentine phosphoprotein.
Heterogeneity among the odontoblast-specific, highly phosphorylated acidic protein dentine phosphoprotein (DPP) obtained from different species has been reported by several investigators. In the present study, the apparent molecular-mass variations in rabbit and mouse DPP were investigated. Extracellular matrix (ECM) DPPs were isolated and characterized. Primary gene products, before post-translational phosphorylation, were analysed based upon translation products produced in a rabbit reticulocyte lysate cell-free system using a polyclonal mouse anti-DPP antibody. Nascent non-phosphorylated DPPs were also identified from intracellular protein extracts. Mouse and rabbit ECM phosphoproteins exhibited a 10 kDa difference in size. However, nascent intracellular or translation products from both species showed the same lower molecular mass (approx. 45 kDa). Furthermore, Northern-blot analysis showed a single mRNA of the same size in both species (approx. 1.6 kb) which contains information for a protein no larger than 50 kDa. Our results indicate that the difference in molecular mass (or electrophoretic behaviour) among DPPs from different species is due to post-translational modifications, in this case phosphorylation.
MacDougall
M
M
Center for Craniofacial Molecular Biology, School of Dentistry, University of Southern California, Los Angeles.
Slavkin
H C
HC
Zeichner-David
M
M
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D002474:Cell-Free System; D003804:Dentin / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D007424:Intracellular Fluid / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000235:genetics; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D015347:RNA Probes; D012333:RNA, Messenger / Q000235:genetics; D011817:Rabbits; D012156:Reticulocytes / Q000502:physiology; D014070:Tooth / Q000737:chemistry / Q000254:growth & development
D010750:Phosphoproteins; D015347:RNA Probes; D012333:RNA, Messenger; C017630:phosphophoryn