Noriaki Ozaki

Characterization of Prismalin-14, a novel matrix protein from the prismatic layer of the Japanese pearl oyster (Pinctada fucata)

The mollusc shell is a hard tissue consisting of calcium carbonate and organic matrices. The organic matrices are believed to play important roles in shell formation. In the present study, we extracted and purified a novel matrix protein, named Prismalin-14, from the acid-insoluble fraction of the prismatic layer of the shell of the Japanese pearl oyster (Pinctada fucata), and determined its whole amino acid sequence by a combination of amino acid sequence analysis and MS analysis of the intact protein and its enzymic digests. Prismalin-14 consisted of 105 amino acid residues, including PIYR repeats, a Gly/Tyr-rich region and N- and C-terminal Asp-rich regions. Prismalin-14 showed inhibitory activity on calcium carbonate precipitation and calcium-binding activity in vitro. The scanning electron microscopy images revealed that Prismalin-14 affected the crystallization of calcium carbonate in vitro. A cDNA encoding Prismalin-14 was cloned and its expression was analysed. The amino acid sequence deduced from the nucleotide sequence of Prismalin-14 cDNA was identical with that determined by peptide sequencing. Northern-blot analysis showed that a Prismalin-14 mRNA was expressed only at the mantle edge. In situ hybridization demonstrated that a Prismalin-14 mRNA was expressed strongly in the inner side of the outer fold of the mantle. These results suggest that Prismalin-14 is a framework protein that plays an important role in the regulation of calcification of the prismatic layer of the shell.

Purification and Structural Determination of a Phosphorylated Peptide with Anti-calcification and Chitin-binding Activities in the Exoskeleton of the Crayfish, Procambarus clarkii

Organic matrices in calcified hard tissues have been considered to control calcification. A matrix peptide, designated CAP-1, was extracted and purified by anionexchange and reverse-phase high performance liquid chromatographies from the exoskeleton of the crayfish, Procambarus clarkii. The amino acid sequence of CAP-1 was determined by mass spectral and sequence analyses of the intact peptide and its enzymatically digested peptides. CAP-1 consisted of 78 amino acid residues, including a phosphoserine residue, and was rich in acidic amino acid residues. CAP-1 had a RebersRiddiford consensus sequence, which is conserved in cuticle proteins from many arthropods. CAP-1 inhibited precipitation of calcium carbonate in an in vitro anticalcification assay dose-dependently, and completelyinhibited it at 3×10-7 M. CAP-1 also showed chitinbinding ability, indicating that this molecule was bifunctional and played an important role in formation of the exoskeleton.

Cloning and expression of a cDNA encoding a matrix peptide associated with calcification in the exoskeleton of the crayfish.

Calcification-associated peptide (CAP)-1 isolated from the exoskeleton of the crayfish, Procambarus clarkii, has anti-calcification activity and chitin-binding ability and is, therefore, considered to be associated with calcification. In this study, a cDNA encoding CAP-1 was cloned and characterized. An open reading frame encoded a pre-propeptide of 99 amino acid residues, which was composed of a signal peptide, a CAP-1 precursor and two-basic amino acid residues at the C-terminus. The dibasic residues were not observed in the natural CAP-1. Expression analyses using Northern blot and RT-PCR revealed that the mRNA encoding CAP-1 was strongly expressed in the epidermal tissue during the postmolt stage, where and when the calcification takes place. These results support that CAP-1 may play an important role in the calcification of the exoskeleton. Based on the nucleotide sequence of the cDNA encoding CAP-1, a recombinant CAP-1 and that carrying the basic residues at the C-terminus were expressed in Escherichia coli. Anti-calcification assay showed that these recombinant peptides were less active than natural CAP-1, indicating that the phosphate group at the 70th residue, Ser, in natural CAP-1 is important for inhibitory activity and that the paired basic residues have some contribution to the elevation of inhibitory activity.

Microtexture of larval shell of oyster, Crassostrea nippona: a FIB-TEM study.

The initial formation and subsequent development of larval shells in marine bivalve, Crassostrea nippona were investigated using the FIB-TEM technique. Fourteen hours after fertilization (the trochophore stage), larvae form an incipient shell of 100-150nm thick with a columnar contrast. Selected-area electron diffraction analysis showed a single-crystal aragonite pattern with the c-axis perpendicular to the shell surface. Plan-view TEM analysis suggested that the shell contains high density of {110} twins, which are the origin of the columnar contrast in the cross-sectional images. 72h after fertilization (the veliger stage), the shell grows up to 1.2-1.4mum thick accompanying an additional granular layer between the preexisting layer and embryo to form a distinctive two-layer structure. The granular layer is also composed of aragonite crystals sharing their c-axes perpendicular to the shell surface, but the crystals are arranged with a flexible rotation around the c-axes and not restricted solely to the {110} twin relation. No evidence to suggest the existence of amorphous calcium carbonate (ACC) was found through the observation. The well-regulated crystallographic properties found in the present sample imply initial shell formation probably via a direct deposition of crystalline aragonite.

Immunolocalization of gastrolith matrix protein (GAMP) in the gastroliths and exoskeleton of crayfish, Procambarus clarkii

Abstract Gastrolith matrix protein (GAMP) is a novel protein purified from gastroliths of the crayfish, Procambarus clarkii, and has been suggested to be associated with calcium carbonate deposition. In the present study, a specific antibody against GAMP was raised and distribution of GAMP immunoreactivity was studied in crayfish gastrolith and exoskeleton. Localization of calcium carbonate in the exoskeleton, determined by silver nitrate staining and energy dispersive X-ray microanalysis, was compared with that of GAMP immunoreactivity. Crystalline forms of calcium carbonate were also determined. SDS-PAGE and Western blotting revealed that the gastrolith extract contained a major band which was GAMP-immunopositive and showed the same mobility as that of purified GAMP. The exoskeleton extract showed smear bands, but no immunoreaction was detected. By using immunohistochemistry, the anti-GAMP antiserum reacted almost uniformly with gastrolith matrix irrespective of gastrolith size. Epithelial cells of the gastrolith disc were also immunopositive. In the exoskeleton, exocuticle was strongly GAMP-immunopositive, whereas the endocuticle and membrane layer was slightly positive. The epicuticle was immunonegative. Calcium carbonate was detected in exocuticle, endocuticle and a part of the membrane layer, but not in the epicuticle. Thus, the distribution of GAMP immunoreactivity roughly corresponded with that of calcium carbonate. X-ray diffraction study showed that calcium carbonate in the gastrolith was amorphous, whereas that in the exoskeleton consisted of calcite crystals. These data indicate that a GAMP-immunoreactive substance is commonly distributed in the mineralized tissues of the crayfish, but may exist in a chemically different form in other tissues.

External stimulation-controllable heat-storage ceramics

Commonly available heat-storage materials cannot usually store the energy for a prolonged period. If a solid material could conserve the accumulated thermal energy, then its heat-storage application potential is considerably widened. Here we report a phase transition material that can conserve the latent heat energy in a wide temperature range, T<530 K and release the heat energy on the application of pressure. This material is stripe-type lambda-trititanium pentoxide, λ-Ti3O5, which exhibits a solid–solid phase transition to beta-trititanium pentoxide, β-Ti3O5. The pressure for conversion is extremely small, only 600 bar (60 MPa) at ambient temperature, and the accumulated heat energy is surprisingly large (230 kJ L−1). Conversely, the pressure-produced beta-trititanium pentoxide transforms to lambda-trititanium pentoxide by heat, light or electric current. That is, the present system exhibits pressure-and-heat, pressure-and-light and pressure-and-current reversible phase transitions. The material may be useful for heat storage, as well as in sensor and switching memory device applications.

Crystallographic alignments in a coccolith (Pleurochrysis carterae) revealed by electron back-scattered diffraction (EBSD)

Abstract Crystal orientations of the sub-micrometer-sized calcite units in oval-shaped coccoliths of a coccolithophore, Pleurochrysis carterae, have been investigated using electron back-scattered diffraction (EBSD). Although the contrast of the acquired EBSD patterns was weak due to the small crystal unit size, the orientations could be uniquely determined from the patterns. The crystal orientations for V- and R-units are close to those reported in a previous work using electron diffraction in a TEM. However, more accurate crystal orientations corresponding to the coccolith morphology were obtained by using EBSD in a SEM. In V-units, the c-axis is declined about 35° from the normal of the coccolith plane and one of the ai-axes is roughly parallel to the coccolith plane. The c-axis in R-units is slightly oblique to the radial direction along the coccolith plane and one of the ai-axes is near vertical to the coccolith plane. The projections of the c-axis of V- and R-units on the coccolith plane deviate considerably from the normal of the coccolith circumference, giving a crystallographic chiral property. The atomic arrangements of calcite contacted with the organic base plate are discussed for both units based on the crystallographic orientations derived from EBSD measurements.

Comparison of crystallographic orientations between living (Emiliania huxleyi and Gephyrocapsa oceanica) and fossil (Watznaueria barnesiae) coccoliths using electron microscopes

Abstract Crystallographic orientations of coccoliths produced by the extant species Emiliania huxleyi and Gephyrocapsa oceanica, and of a fossil cocccolith, Watzunaueria barnesiae, all of which are mainly composed of calcite crystals with horizontally oriented c axes (termed R-units), were investigated using two electron diffraction techniques. According to electron backscattered diffraction (EBSD) analyses, the c-axis inclinations of all R-units were oriented about 10-30° from the sample substrate, which is approximately parallel to the organic base plate of the coccolith. However, the directions are toward the coccolith exterior in living coccoliths but toward the interior in fossil coccoliths. The crystallographic orientations of calcite crystals characterized by sub-vertically oriented c axes (termed V-units) were determined only for W. barnesiae and were similar to those of V-units in another living cococlith, Pleurochrysis carterae. Highly regulated crystallographic orientation and consistent chirality were evidenced for all the coccoliths with only a few degrees of variations by Kikuchi patterns analyses from TEM. To determine the indices of the crystallographic plane and edge direction that constitute distal and proximal shield elements, SEM stereo-photogrammetry in combination with EBSD analyses was applied. In the living coccoliths both shields contain the c-axis and the surface is estimated to be {21̅1̅0} with [481] the longer peripheral edge. On the other hand, the two shield surfaces of W. barnesiae are evaluated {101̅4} and the distal shield surface is surrounded by clear [481] edges. This indicates that the crystallography and morphology of R-units were not fixed for the past 230 million years. Based on these results, the calcite nucleation mechanisms are discussed with respect to the atomic arrangements on the organic template through all the coccoliths.

The Coprinopsis cinerea septin Cc.Cdc3 is involved in stipe cell elongation.

We have identified and characterized a Coprinopsis cinerea mutant defective in stipe elongation during fruiting body development. In the wild-type, stipe cells elongate at the maturation stage of fruiting, resulting in very slender cells. In the mutant, the stipe cells fail to elongate, but become rather globular at the maturation stage. We found that the mutant phenotype is rescued by a gene encoding a homolog of Saccharomyces cerevisiae CDC3 septin, Cc.Cdc3. The C. cinerea genome includes 6 septin genes, 5 of which, including Cc.cdc3, are highly transcribed during stipe elongation in the wild type. In the mutant, the level of Cc.cdc3 transcription in the stipe cells remains the same as that in the mycelium, and the level of Cc.cdc10 transcription is approximately 100 times lower than that in the wild-type stipe cells. No increase in transcription of Cc.cdc3 in the mutant may be due to the fact that the Cc.cdc3 gene has a 4-base pair insertion in its promoter and/or that the promoter region is methylated in the mutant. Overexpressed EGFP-Cc.Cdc3 fusion protein rescues the stipe elongation in the transformants, localizes to the cell cortex and assembles into abundant thin filaments in the elongating stipe cells. In contrast, in vegetative hyphae, EGFP-Cc.Cdc3 is localized to the hyphal tips of the apical cells of hyphae. Cellular defects in the mutant, combined with the localization of EGFP-Cc.Cdc3, suggest that septin filaments in the cell cortex provide the localized rigidity to the plasma membrane and allow cells to elongate cylindrically.

Isolation and Characterization of 2-Nitroimidazole Produced by Streptomyces Species as an Inhibitor of Both Carbonic Anhydrase and Shell Formation in the Barnacle Balanus amphitrite

Abstract: Carbonic anhydrase is thought to be involved in the process of calcium carbonate deposition in calcified tissues of many organisms. Barnacles form hard calcified shells for protection against predation, and represent a class of marine-fouling animals. In order to inhibit barnacle growth by inhibiting shell formation, we searched for carbonic anhydrase inhibitors from microbial secondary metabolites. A simple assay for assessing carbonic-anhydrase-inhibiting activity was developed. Screening of many microorganisms isolated from soil with this assay resulted in a microbial strain that produced a carbonic anhydrase inhibitor. This strain was identified as Streptomyces eurocidicus mf294. The inhibitor was isolated through 4 purification steps and identified as 2-nitroimidazole on the basis of spectroscopic data. 2-Nitroimidazole inhibited barnacle carbonic anhydrase dose-dependently and complete inhibition was reached at the concentration of 1 × 10−5 M. 2-Nitroimidazole did not affect settlement or metamorphosis of barnacle larvae, but inhibited shell formation at concentrations higher than 1 × 10−4 M. These findings strongly support the idea that carbonic anhydrase is involved in calcification.