The carboxyl-terminal domain of phosphophoryn contains unique extended triplet amino acid repeat sequences forming ordered carboxyl-phosphate interaction ridges that may be essential in the biomineralization process.
Phosphophoryns (PPs), a family of Asp and Ser(P)-rich dentin proteins, are considered to be archetypal regulators of several aspects of extracellular matrix (ECM) biomineralization. We have cloned a rat incisor PP gene, Dmp2, from our odontoblast cDNA library and localized it to mouse chromosome 5q21 within 2 centimorgans of Dmp1, another tooth-specific ECM protein. The carboxyl-terminal region of Dmp2 protein (60 residue % Ser, 31 residue % Asp) is divided into two domains, one with unique repetitive blocks of [DSS]n,3</=14, the other with [SD]m = 2,3. Conformational analysis shows the phosphorylated form of the [DS*S*]n repeats to have a unique structure with well defined ridges of phosphates and carboxyls available for counter ion binding. The [S*D]m domains have different phosphate and carboxylate interaction edges and thus different calcium ion and apatite surface binding properties. These two domains and the colocalization of Dmp1 and Dmp2 genes at a position equivalent to the dentinogenesis imperfecta type II location on human 4q21 all suggest that the PPs are indeed involved in some aspect of ECM mineralization.
George
A
A
Northwestern University, Chicago, Illinois 60611, USA. aveis@nwu.edu
Bannon
L
L
Sabsay
B
B
Dillon
J W
JW
Malone
J
J
Veis
A
A
Jenkins
N A
NA
Gilbert
D J
DJ
Copeland
N G
NG
D000595:Amino Acid Sequence; D000818:Animals; D002113:Calcification, Physiologic; D002874:Chromosome Mapping; D003804:Dentin / Q000378:metabolism; D003811:Dentinogenesis Imperfecta / Q000235:genetics; D016326:Extracellular Matrix Proteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D015870:Gene Expression; D051379:Mice; D008969:Molecular Sequence Data; D009804:Odontoblasts / Q000502:physiology; D010750:Phosphoproteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D011487:Protein Conformation; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D012091:Repetitive Sequences, Nucleic Acid; D014018:Tissue Distribution
D016326:Extracellular Matrix Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; C017630:phosphophoryn