Silicification: The Processes by Which Organisms Capture and Mineralize Silica

Perry, Carole C.

doi:10.2113/0540291

Cited by 132 publications

(87 citation statements)

References 87 publications

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“…While one set of molecules is seen in a pI range between 4.7 and 4.2, the second set is characterized by pI values between 6.8 and 7.3. It might be speculated that the proteins are modified by differential phosphorylation and/or glutamylation or tyrosination, as described for the silica-depositing proteins in diatoms (reviewed in Perry, 2003). Further functional studies will solve the question of why these molecules exist only in the central region of the Monorhaphis giant basal spicules.…”

Section: Discussionmentioning

confidence: 98%

“…So far data indicate that demosponges have the unique ability to synthesize their siliceous skeleton enzymatically (Shimizu et al, 1998;Cha et al, 1999), in contrast to other organisms that deposit bio-silica in a template-controlled manner (reviewed in Perry, 2003). The responsible enzyme, silicatein, was first described by the group of Morse in the marine demosponge Tethya aurantium (Cha et al, 1999) and subsequently also identified in other demosponges, most prominently in Suberites domuncula (Krasko et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

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Identification of a silicatein(-related) protease in the giant spicules of the deep-sea hexactinellidMonorhaphis chuni

Müller

Boreiko

Schloßmacher

et al. 2008

Journal of Experimental Biology

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SUMMARYSilicateins, members of the cathepsin L family, are enzymes that have been shown to be involved in the biosynthesis/condensation of biosilica in spicules from Demospongiae (phylum Porifera), e.g. Tethya aurantium and Suberites domuncula. The class Hexactinellida also forms spicules from this inorganic material. This class of sponges includes species that form the largest biogenic silica structures on earth. The giant basal spicules from the hexactinellids Monorhaphis chuni and Monorhaphis intermedia can reach lengths of up to 3·m and diameters of 10·mm. The giant spicules as well as the tauactines consist of a biosilica shell that surrounds the axial canal, which harbours the axial filament, in regular concentric, lamellar layers, suggesting an appositional growth of the spicules. The lamellae contain 27·kDa proteins, which undergo post-translational modification (phosphorylation), while total spicule extracts contain additional 70·kDa proteins. The 27·kDa proteins cross-reacted with anti-silicatein antibodies. The extracts of spicules from the hexactinellid Monorhaphis displayed proteolytic activity like the silicateins from the demosponge S. domuncula. Since the proteolytic activity in spicule extracts from both classes of sponge could be sensitively inhibited by E-64 (a specific cysteine proteinase inhibitor), we used a labelled E-64 sample as a probe to identify the protein that bound to this inhibitor on a blot. The experiments revealed that the labelled E-64 selectively recognized the 27·kDa protein. Our data strongly suggest that silicatein(-related) molecules are also present in Hexactinellida. These new results are considered to also be of impact for applied biotechnological studies.

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Section: Discussionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Identification of a silicatein(-related) protease in the giant spicules of the deep-sea hexactinellidMonorhaphis chuni

Müller

Boreiko

Schloßmacher

et al. 2008

Journal of Experimental Biology

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“…One explanation might be that the much higher concentration of Na than K in seawater (Kennish 1994) causes an exchange to occur with respect to the initially synthesized K + -silicate to Na + -silicate, after exposure of the siliceous spicules to the surrounding milieu. However, another explanation might also be possible: Iler (1979) and Perry (2003) have demonstrated that, in the presence of smaller cations (e.g., Na + ), a faster condensation rate of silica occurs, in comparison with the rate measured with larger cations (e.g., K + ). This view is supported by studies with diatoms in which Si transport into cells has been proposed to be driven by Na + -gradients generated and maintained across the membrane by the activity of a Na + /K + -ATPase (Sullivan 1986).…”

Section: -------------------------------------------mentioning

confidence: 99%

Formation of giant spicules in the deep-sea hexactinellid Monorhaphis chuni (Schulze 1904): electron-microscopic and biochemical studies

et al. 2007

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The siliceous sponge Monorhaphis chuni (Hexactinellida) synthesizes the largest biosilica structures on earth (3 m). Scanning electron microscopy has shown that these spicules are regularly composed of concentrically arranged lamellae (width: 3-10 μm). Between 400 and 600 lamellae have been counted in one giant basal spicule. An axial canal (diameter:~2 μm) is located in the center of the spicules; it harbors the axial filament and is surrounded by an axial cylinder (100-150 μm) of electron-dense homogeneous silica. During dissolution of the spicules with hydrofluoric acid, the axial filament is first released followed by the release of a proteinaceous tubule. Two major proteins (150 kDa and 35 kDa) have been visualized, together with a 24-kDa protein that cross-reacts with antibodies against silicatein. The spicules are surrounded by a collagen net, and the existence of a hexactinellidan collagen gene has been demonstrated by cloning it from Aphrocallistes vastus. During the axial growth of the spicules, silicatein or the silicatein-related protein is proposed to become associated with the surface of the spicules and to be finally internalized through the apical opening to associate with the axial filament. Based on the data gathered here, we suggest that, in the Hexactinellida, the growth of the spicules is mediated by silicatein or by a silicatein-related protein, with the orientation of biosilica deposition being controlled by lectin and collagen.

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“…The observation that in the cone region the spicules are composed of silica spheres, while these skeletal elements in the socket bundles are of the solid state strongly suggest that the diVerent ultrastructures of both silica forms is due to their water content. It is well established that during precipitation of silicon in water a transition from the ortho-form of silicic acid via its meta-form to the amorphous, hydrated, and polymerized silicas of the general formula SiO 2 ·nH 2 O occurs (Perry, 2003;Williams, 1986). This process is paralleled with a loss of water from the condensation products of silicic acid.…”

Section: Discussionmentioning

confidence: 99%

Magnetic resonance imaging of the siliceous skeleton of the demosponge Lubomirskia baicalensis

Müller

Kaluzhnaya

Беликов

et al. 2006

Journal of Structural Biology

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The skeletal elements (spicules) of the demosponge Lubomirskia baicalensis were analyzed; they are composed of amorphous, noncrystalline silica, and contain in a central axial canal the axial Wlament which consists of the enzyme silicatein. The axial Wlament, that orients the spicule in its longitudinal axis exists also in the center of the spines which decorate the spicule. During growth of the sponge, new serially arranged modules which are formed from longitudinally arranged spicule bundles are added at the tip of the branches. X-ray analysis revealed that these serial modules are separated from each other by septate zones (annuli). We describe that the longitudinal bundles of spicules of a new module originate from the apex of the earlier module from where they protrude. A cross section through the oscular/apical-basal axis shows that the bundle rays are organized in a concentric and radiate pattern. High resolution magnetic resonance microimaging studies showed that the silica spheres of the spicules in the cone region contain high amounts of 'mobile' water. We conclude that the radiate accretive growth pattern of sponges is initiated in the apical region (cones) by newly growing spicules which are characterized by high amounts of 'mobile' water; subsequently spicule bundles are formed laterally around the cones. 

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Silicification: The Processes by Which Organisms Capture and Mineralize Silica

Cited by 132 publications

References 87 publications

Identification of a silicatein(-related) protease in the giant spicules of the deep-sea hexactinellidMonorhaphis chuni

Identification of a silicatein(-related) protease in the giant spicules of the deep-sea hexactinellidMonorhaphis chuni

Formation of giant spicules in the deep-sea hexactinellid Monorhaphis chuni (Schulze 1904): electron-microscopic and biochemical studies

Magnetic resonance imaging of the siliceous skeleton of the demosponge Lubomirskia baicalensis

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