Document Detail

Hierarchical composition of the axial filament from spicules of the siliceous sponge Suberites domuncula: from biosilica-synthesizing nanofibrils to structure- and morphology-guiding triangular stems.
MedLine Citation:
PMID:  23135475     Owner:  NLM     Status:  Publisher    
The major structural and enzymatically active protein in spicules from siliceous sponges, e.g., for Suberites domuncula studied here, is silicatein. Silicatein has been established to be the key enzyme that catalyzes the formation of biosilica, a polymer that represents the inorganic scaffold for the spicule. In the present study, it is shown, by application of high-resolution transmission and scanning transmission electron microscopy that, during the initial phase of spicule synthesis, nanofibrils with a diameter of around 10 nm are formed that comprise bundles of between 10 and 20 nanofibrils. In intracellular vacuoles, silicasomes, the nanofibrils form polar structures with a pointed tip and a blunt end. In a time-dependent manner, these nanofibrillar bundles become embedded into a Si-rich matrix, indicative for the formation of biosilica via silicatein molecules that form the nanofibrils. These biosilicified nanofibrillar bundles become extruded from the intracellular space, where they are located in the silicasomes, to the extracellular environment by an evagination process, during which a cellular protrusion forms the axial canal in the growing spicule. The nanofibrillar bundles condense and progressively form the axial filament that becomes localized in the extracellular space. It is concluded that the silicatein-composing nanofibrils act not only as enzymatic silica bio-condensing platforms but also as a structure-giving guidance for the growing spicule.
Werner E G Müller; Enrico Mugnaioli; Heinz C Schröder; Ute Schloßmacher; Marco Giovine; Ute Kolb; Xiaohong Wang
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-11-8
Journal Detail:
Title:  Cell and tissue research     Volume:  -     ISSN:  1432-0878     ISO Abbreviation:  Cell Tissue Res.     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-8     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0417625     Medline TA:  Cell Tissue Res     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
ERC Advanced Investigator Grant Research Group at Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, 55128, Mainz, Germany,
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