Silacidins: Highly Acidic Phosphopeptides from Diatom Shells Assist in Silica Precipitation In Vitro

Wenzl, Stephan; Hett, Robert; Richthammer, Patrick; Sumper, Manfred

doi:10.1002/ange.200704994

Cited by 151 publications

(108 citation statements)

References 29 publications

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“…The Arg-X-Leu motif is also present in the precursor proteins of silaffins, silacidins, and other biosilica-associated diatom proteins, where it is the recognition site for proteolytic cleavage at the C-terminus of the leucine residue (3,(10)(11)(12)(13). Therefore, it seems likely that cingulins also undergo proteolytic processing, and thus the mature proteins probably lack the RXL domains.…”

Section: Resultsmentioning

confidence: 99%

Nanopatterned protein microrings from a diatom that direct silica morphogenesis

Scheffel

Poulsen²,

Shian³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

184

236

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Diatoms are eukaryotic microalgae that produce species-specifically structured cell walls made of SiO 2 (silica). Formation of the intricate silica structures of diatoms is regarded as a paradigm for biomolecule-controlled self-assembly of three-dimensional, nano-to microscale-patterned inorganic materials. Silica formation involves long-chain polyamines and phosphoproteins (silaffins and silacidins), which are readily soluble in water, and spontaneously form dynamic supramolecular assemblies that accelerate silica deposition and influence silica morphogenesis in vitro. However, synthesis of diatom-like silica structure in vitro has not yet been accomplished, indicating that additional components are required. Here we describe the discovery and intracellular location of six novel proteins (cingulins) that are integral components of a silica-forming organic matrix (microrings) in the diatom Thalassiosira pseudonana. The cingulin-containing microrings are specifically associated with girdle bands, which constitute a substantial part of diatom biosilica. Remarkably, the microrings exhibit protein-based nanopatterns that closely resemble characteristic features of the girdle band silica nanopatterns. Upon the addition of silicic acid the microrings become rapidly mineralized in vitro generating nanopatterned silica replicas of the microring structures. A silica-forming organic matrix with characteristic nanopatterns was also discovered in the diatom Coscinodiscus wailesii, which suggests that preassembled protein-based templates might be general components of the cellular machinery for silica morphogenesis in diatoms. These data provide fundamentally new insight into the molecular mechanisms of biological silica morphogenesis, and may lead to the development of self-assembled 3D mineral forming protein scaffolds with designed nanopatterns for a host of applications in nanotechnology.biomineralization | GFP | silica deposition vesicle | bioinformatics

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Section: Resultsmentioning

confidence: 99%

Nanopatterned protein microrings from a diatom that direct silica morphogenesis

Scheffel

Poulsen²,

Shian³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

184

236

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“…silaffins [66] and silacidins [67]). None of these, other than SITs, were identified in our sequence data.…”

Section: (F ) Evolutionary Implications For Biosilicificationmentioning

confidence: 99%

A family of diatom-like silicon transporters in the siliceous loricate choanoflagellates

et al. 2013

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Biosilicification is widespread across the eukaryotes and requires concentration of silicon in intracellular vesicles. Knowledge of the molecular mechanisms underlying this process remains limited, with unrelated silicontransporting proteins found in the eukaryotic clades previously studied. Here, we report the identification of silicon transporter (SIT)-type genes from the siliceous loricate choanoflagellates Stephanoeca diplocostata and Diaphanoeca grandis. Until now, the SIT gene family has been identified only in diatoms and other siliceous stramenopiles, which are distantly related to choanoflagellates among the eukaryotes. This is the first evidence of similarity between SITs from different eukaryotic supergroups. Phylogenetic analysis indicates that choanoflagellate and stramenopile SITs form distinct monophyletic groups. The absence of putative SIT genes in any other eukaryotic groups, including non-siliceous choanoflagellates, leads us to propose that SIT genes underwent a lateral gene transfer event between stramenopiles and loricate choanoflagellates. We suggest that the incorporation of a foreign SIT gene into the stramenopile or choanoflagellate genome resulted in a major metabolic change: the acquisition of biomineralized silica structures. This hypothesis implies that biosilicification has evolved multiple times independently in the eukaryotes, and paves the way for a better understanding of the biochemical basis of silicon transport through identification of conserved sequence motifs.

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“…LiDSI involves genetic engineering of diatoms, which are unicellular eukaryotic algae that produce silica-based cell walls. Diatom silica formation depends on specific proteins (silaffins, silacidins, cingulins) that remain permanently associated within the silica in vivo (23,34,41). It has previously been demonstrated that expression in the diatom Thalassiosira pseudonana of a fusion protein consisting of the silaffin tpSil3 and the bacterial enzyme hydroxylaminobenzene mutase (HabB) generates diatom strains that exhibit biosilicaassociated HabB activity (31).…”

mentioning

confidence: 99%

Live Diatom Silica Immobilization of Multimeric and Redox-Active Enzymes

Sheppard

Scheffel

Poulsen

et al. 2012

Appl Environ Microbiol

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Living organisms are adept in forming inorganic materials (biominerals) with unique structures and properties that exceed the capabilities of engineered materials. Biomimetic materials syntheses are being developed that aim at replicating the advantageous properties of biominerals in vitro and endow them with additional functionalities. Recently, proof-of-concept was provided for an alternative approach that allows for the production of biomineral-based functional materials in vivo. In this approach, the cellular machinery for the biosynthesis of nano-/micropatterned SiO 2 (silica) structures in diatoms was genetically engineered to incorporate a monomeric, cofactor-independent ("simple") enzyme, HabB, into diatom silica. In the present work, it is demonstrated that this approach is also applicable for enzymes with "complex" activity requirements, including oligomerization, metal ions, organic redox cofactors, and posttranslational modifications. Functional expression of the enzymes ␤-glucuronidase, glucose oxidase, galactose oxidase, and horseradish peroxidase in the diatom Thalassiosira pseudonana was accomplished, and 66 to 78% of the expressed enzymes were stably incorporated into the biosilica. The in vivo incorporated enzymes represent approximately 0.1% (wt/wt) of the diatom biosilica and are stabilized against denaturation and proteolytic degradation. Furthermore, it is demonstrated that the gene construct for in vivo immobilization of glucose oxidase can be utilized as the first negative selection marker for diatom genetic engineering.

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Silacidins: Highly Acidic Phosphopeptides from Diatom Shells Assist in Silica Precipitation In Vitro

Cited by 151 publications

References 29 publications

Nanopatterned protein microrings from a diatom that direct silica morphogenesis

Nanopatterned protein microrings from a diatom that direct silica morphogenesis

A family of diatom-like silicon transporters in the siliceous loricate choanoflagellates

Live Diatom Silica Immobilization of Multimeric and Redox-Active Enzymes

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