Evolution of Nacre: Biochemistry and Proteomics of the Shell Organic Matrix of the Cephalopod Nautilus macromphalus

In mollusks, one of the most widely studied shell textures is nacre, the lustrous aragonitic layer that constitutes the internal components of the shells of several bivalves, a few gastropods, and one cephalopod: the nautilus. Nacre contains a minor or- ganic fraction, which displays a wide range of functions in relation to the biomineralization process. Here, we have biochemi- cally characterized the nacre matrix of the cephalopod Nautilus macromphalus. The acid-soluble matrix contains a mixture of polydisperse and discrete proteins and glycoproteins, which interact with the formation of calcite crystals. In addition, a few bind calcium ions. Furthermore, we have used a proteomic approach, which was applied to the acetic acid-soluble and insoluble shell matrices, as well as to spots obtained after 2D gel electrophoresis. Our data demonstrate that the insoluble and soluble matrices, although different in their bulk monosacchar- ide and amino acid compositions, contain numerous shared peptides. Strikingly, most of the obtained partial sequences are entirely new. A few only partly match with bivalvian nacre pro- teins. Our findings have implications for knowledge of the long-term evolution of molluskan nacre matrices.


An interesting feature, of these molluscan protiens , is the Tyrosinase domains which seems to be unique to molluscs, one possibility is its realtionship to hemocyanins

Tyrosinase () PUBMED:3130643 is a copper monooxygenases that catalyzes the hydroxylation of monophenols and the oxidation of o-diphenols to o-quinols. This enzyme, found in prokaryotes as well as in eukaryotes, is involved in the formation of pigments such as melanins and other polyphenolic compounds. Tyrosinase binds two copper ions (CuA and CuB). Each of the two copper ions has been shown PUBMED:1901488 to be bound by three conserved histidines residues. The regions around these copper-binding ligands are well conserved and also shared by some hemocyanins, which are copper-containing oxygen carriers from the hemolymph of many molluscs and arthropods PUBMED:2664531, PUBMED:1898774. At least two proteins related to tyrosinase are known to exist in mammals, and include TRP-1 (TYRP1) PUBMED:7813420, which is responsible for the conversion of 5,6-dihydro-xyindole-2-carboxylic acid (DHICA) to indole-5,6-quinone-2-carboxylic acid; and TRP-2 (TYRP2) PUBMED:1537334, which is the melanogenic enzyme  DOPAchrome tautomerase () that catalyzes the conversion of DOPAchrome to DHICA. TRP-2 differs from tyrosinases and TRP-1 in that it binds two zinc ions instead of copper PUBMED:7980602. Other proteins that belong to this family are plant polyphenol oxidases (PPO) (), which catalyze the oxidation
of mono- and o-diphenols to o-diquinones PUBMED:1391768; and  Caenorhabditis elegans hypothetical protein C02C2.1.

check out these proteins full of Tyrosinase 😉






Dentin Matrix Protein 1 Regulates Dentin Sialophosphoprotein Gene Transcription during Early Odontoblast Differentiation

Dentin matrix protein 1 regulates dentin sialophosphoprotein gene transcription during early odontoblast differentiation.

Dentin mineralization requires transcriptional mechanisms to induce a cascade of gene expression for progressive develop- ment of the odontoblast phenotype. During cytodifferentiation of odontoblasts there is a constant change of actively tran- scribed genes. Thus, tissue-specific matrix genes that are silenced in early differentiation are expressed during the termi- nal differentiation process. Dentin sialophosphoprotein (DSPP) is an extracellular matrix, prototypical dentin, and a bone-spe- cific gene, however, the molecular mechanisms by which it is temporally and spatially regulated are not clear. In this report, we demonstrate that dentin matrix protein 1 (DMP1), which is localized in the nucleus during early differentiation of odonto- blasts, is able to bind specifically with the DSPP promoter and activate its transcription. We have identified the specific pro- moter sequence that binds specifically to the carboxyl end of DMP1. The DNA binding domain in DMP1 resides between amino acids 420 and 489. A chromatin immunoprecipitation assay confirmed the in vivo association of DMP1 with the DSPP promoter. Interactions between DMP1 and DSPP promoter thus provide the foundation to understand how DMP1 regulates the expression of the DSPP gene.


Carbonic anhydrase II regulates differentiation of ameloblasts via intracellular pH-dependent JNK signaling pathway

Differentiation of ameloblasts from undifferentiated epithelial cells is controlled by diverse growth factors, as well as interactions between epithelium and mesenchyme. However, there is a considerable lack of knowledge regarding the precise mechanisms that control ameloblast differentiation and enamel biomineralization. We found that the expression level of carbonic anhydrase II (CAII) is strongly up-regulated in parallel with differentiation of enamel epithelium tissues, while the enzyme activity of CA was also increased along with differentiation in ameloblast primary cultures. The expression level of amelogenin, a marker of secretory-stage ameloblasts, was enhanced by ethoxzolamide (EZA), a CA inhibitor, as well as CAII antisense (CAIIAS), whereas the expression of enamel matrix serine proteinase-1 (EMSP-1), a marker for maturation-stage ameloblasts, was suppressed by both. These agents also promoted ameloblast proliferation. In addition, inhibition of ameloblast differentiation by EZA and CAIIAS was confirmed using tooth germ organ cultures. Furthermore, EZA and CAIIAS elevated intracellular pH in ameloblasts, while experimental decreases in intracellular pH abolished the effect of CAIIAS on ameloblasts and triggered the activation of c-Jun N-terminal kinase (JNK). SP600125, a JNK inhibitor, abrogated the response of ameloblasts to an experimental decrease in intracellular pH, while the inhibition of JNK also impaired ameloblast differentiation. These results suggest a novel role for CAII during amelogenesis, that is, controlling the differentiation of ameloblasts. Regulation of intracellular pH, followed by activation of the JNK signaling pathway, may be responsible for the effects of CAII on ameloblasts


Dentin Sialophosphoprotein (DSPP) in Biomineralization

Two of the proteins found in significant quantity in the extracellular matrix (ECM) of dentin are dentin phosphoprotein (DPP) and dentin sialoprotein (DSP). DPP, the most abundant of the non-collagenous proteins in dentin is an unusually polyanionic protein, containing a large number of aspartic acids (Asp) and phosphoserines (Pse) in the repeating sequences of (Asp-Pse)n. and (Asp-Pse-Pse)n. The many negatively charged regions of DPP are thought to promote mineralization by binding calcium and presenting it to collagen fibers at the mineralization front during the formation of dentin. This purported role of DPP is supported by a sizeable pool of in vitro mineralization data showing that DPP is an important initiator and modulator for the formation and growth of hydroxyapatite crystals. Quite differently, DSP is a glycoprotein, with little or no phosphate. DPP and DSP are the cleavage products of dentin sialophosphoprotein (DSPP). Human and mouse genetic studies have demonstrated that mutations in, or knockout of, the Dspp gene result in mineralization defects in dentin and/or bone. The discoveries in the past 40 years with regard to DPP, DSP and DSPP have greatly enhanced our understanding of biomineralization and set a new stage for future studies. In this review, we summarize the important and new developments made in the past four decades regarding the structure and regulation of the DSPP gene, the biochemical characteristics of DSPP, DPP and DSP, as well as the cell/tissue localizations and functions of these molecules.


Of course, we know what is coming next right? 😉


MOLECULAR BIOMINERALIZATION: FROM GENE TO STRUCTURES AND BIO-PRODUCTS Werner E.G. Müller Institute for Physiological Chemistry, Johannes Gutenberg University, Medical School, Mainz, Germany, wmueller@uni-mainz.de. During animal evolution, biomolecules (e.g., secondary metabolites) and biomaterials (e.g., biominerals) were selected for higher biological efficiency and superior physical properties. In the last 40 years secondary metabolites hadabeen exploited for biomedical applications, resulting in the development of 9-β-Darabinofuranosyladenosine as a first active pharmaceutical ingredient by us[1]. Only recently the fundament for the biotechnological exploitation of biominerals has been laid by the demonstration that the formation of inorganic deposits within organisms is governed by organic molecules or templates. During INORGANIC MINERALIZATION, the conversion of monomers into solid-state material usually occurs through endothermic reactions. Differently for the initiation and maintenance of BIOMINERAL FORMATION, bioseeds and/or organic surfaces and matrices are required. Two categories can be distinguished: (a) biologically induced mineralization and (b) biologically controlled mineralization. During the seed phase of BIOLOGICALLY INDUCED MINERALIZATION processes, organic polymers allow controlled nucleation and crystal growth. For example, marine snow and coccoliths/coccospheres have mineralization potential. Coccoliths/coccospheres have recently been implied by us in the formation of ferromanganese nodules/crusts in the deep sea[2]. These particles/aggregates act as bioseeds and mediate deposition of inorganic materials from an environment that contains the inorganic precursors at nonsaturated conditions. BIOLOGICALLY CONTROLLED MINERALIZATION describes a process that is guided along bioseeds and organic matrices. These organic molecules function as bioseeds and also as scaffold during the subsequent growth phase; examples are mammalian teeth or bones. A special form of biologically controlled mineralization is the enzymatically controlled biomineralization that has been described for the biosilicification process in siliceous sponges[3]. In these animals the enzyme silicatein is catalytically involved in the formation of biosilica. Since then, learning from sponges and mastering nature’s concept of siliceous skeletal element formation inspired many strategies that aim to biofabricate minerals. The first progress has been made in biomedicine and electronics, providing us with strong indications about the power and potential of this new technology[4]. References [1] Müller, W.E.G., Zahn, R.K., K., Falke, D. 1977. Inhibition of herpesvirus DNA-synthesis by 9-β-D-arabinofuranosyladenosine in vitro and in vivo. Ann N Y Acad Sci 284:34-48 [2] Wang, X.H., Müller, W.E.G. 2009. Marine biominerals: perspectives and challenges for polymetallic nodules and crusts. Trends Biotechnol 27:375- 383. [3] Wang, X.H., Schröder, H.C., Müller, W.E.G. 2009. Giant siliceous spicules from the deep-sea glass sponge Monorhaphis chuni: morphology, biochemistry, and molecular biology. Int Rev Cell Mol Biol 273:69-115. [4] Müller, W.E.G., Wang, X.H., Cui, F.Z., Jochum, K.P., Tremel, W., Bill, J., Schröder, H.C., Wiens, M. 2009. Sponge spicules as blueprints for the biofabrication of inorganic-organic composites and biomaterials. Appl Microbiol Biotechnol 83:397-413.