Intrinsically Disordered and Pliable Starmaker-Like Protein from Medaka (Oryzias latipes) Controls the Formation of Calcium Carbonate Crystals

Abstract

Fish otoliths, biominerals composed of calcium carbonate with a small amount of organic matrix, are involved in the functioning of the inner ear. Starmaker (Stm) from zebrafish (Danio rerio) was the first protein found to be capable of controlling the formation of otoliths. Recently, a gene was identified encoding the Starmaker-like (Stm-l) protein from medaka (Oryzias latipes), a putative homologue of Stm and human dentine sialophosphoprotein. Although there is no sequence similarity between Stm-l and Stm, Stm-l was suggested to be involved in the biomineralization of otoliths, as had been observed for Stm even before. The molecular properties and functioning of Stm-l as a putative regulatory protein in otolith formation have not been characterized yet. A comprehensive biochemical and biophysical analysis of recombinant Stm-l, along with in silico examinations, indicated that Stm-l exhibits properties of a coil-like intrinsically disordered protein. Stm-l possesses an elongated and pliable structure that is able to adopt a more ordered and rigid conformation under the influence of different factors. An in vitro assay of the biomineralization activity of Stm-l indicated that Stm-l affected the size, shape and number of calcium carbonate crystals. The functional significance of intrinsically disordered properties of Stm-l and the possible role of this protein in controlling the formation of calcium carbonate crystals is discussed.

Not All Inner Ears are the Same: Otolith Matrix Proteins in the Inner Ear of Sub‐Adult Cichlid Fish, Oreochromis Mossambicus, Reveal Insights Into the Biomineralization Process

“…Surprisingly, we could found no evidence for the occurrence of the known OMP starmaker, as described for zebrafish, its orthologous protein OMM‐64 in Salmo salar and of the starmaker‐like protein in medaka (Söllner et al, ; Tohse et al, ; Bajoghli et al, ; Różycka et al, ). Starmaker and its orthologs show similarities to human‐dentin and are members of the secretory calcium‐binding phosphoprotein family (Söllner et al, ).…”

“…Starmaker and its orthologs show similarities to human‐dentin and are members of the secretory calcium‐binding phosphoprotein family (Söllner et al, ). However, calcium‐binding phosphoproteins are poorly conserved and therefore their identification and characterization is difficult (Kawasaki and Weiss, ; Różycka et al, ). Thus in a screening of the sequenced genome of the Nile tilapia ( Oreochromis niloticus ), we also found no hints for the occurrence of a starmaker ortholog in the Oreochromis genus.…”

The Proline/Glycine-Rich Region of the Biofilm Adhesion Protein Aap Forms an Extended Stalk that Resists Compaction

“…5c). Although this is not a typical response, other IDPs have been reported that show essentially no change in their far-UV spectra with increasing TMAO, including myelin basic protein (MyBP) [94] and starmaker-like protein (Stm-1) involved in biomineralization of otoliths [95]. Like PGR, each of these proteins is highly charged (28-47% of the residues are charged), although MyBP and Stm-1 have only 3-6% proline content compared to 29% for PGR.…”

In vivoandin vitroanalysis of starmaker activity in zebrafish otolith biomineralization

“…The effect of StmN and StmC on calcium carbonate crystallization was investigated using a slow diffusion method previously used for full-length Stm (18,35). Crystallization solution (300 ml) consisted of 0.155 or 1.55 mM concentration of protein fragments in TNaG buffer and 10 mM CaCl 2 .…”