Properties of the (DSS)n triplet repeat domain of rat dentin phosphophoryn.
Phosphophoryns (PPs) are unique aspartic acid and phosphoserine-rich proteins present in all species of dentin. Rat incisor odontoblast cDNA libraries contain messages encoding several acidic phosphorylated, serine-rich proteins. At least two of these share a common C-terminal domain coding region sequence. The polypeptide sequences in the N-terminal direction immediately adjacent to the conserved C-terminal domains of these two proteins (DMP2, DMP3) are distinctly different. In this domain, the DMP2 has extensive sequences of (DSS)n repeats with n as large as 24. DMP3 has fewer and shorter triplet sequences, n = 3, 4. The major rat incisor PPs (90-95 kDa) probably have the (DSS)n>>3. We propose that the name phosphophoryn be reserved for the extracellular matrix proteins with these extended repeats. DMPI, although strongly acidic, does not fit this category. If the S residues are phosphorylated and n > 3, conformational energy minimization computations show the (DSS)n sequence to assume a unique extended structure with parallel arrays of carboxylate and phosphate groups which may function as Ca2+ ion interaction edges. The phosphorylation of recombinant DMP2 C-terminal domain by various kinases has been examined. The repeat domains are not direct substrates for the CK2-like kinases but the kinases act in concert, so that the phosphorylation is hierarchical, apparently controlled by the presence of specific interruptions between the triplet domains.
Veis
A
A
Division of Oral Biology, Northwestern University Dental School, Chicago, Illinois, USA. aveis@nwu.edu
Wei
K
K
Sfeir
C
C
George
A
A
Malone
J
J
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D047390:Casein Kinase II; D047388:Casein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D003804:Dentin / Q000737:chemistry* / Q000378:metabolism; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D011487:Protein Conformation; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D012091:Repetitive Sequences, Nucleic Acid
D017931:DNA Primers; D010750:Phosphoproteins; C017630:phosphophoryn; D011494:Protein Kinases; D047390:Casein Kinase II; D047388:Casein Kinases; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases