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Logo of jbcThe Journal of Biological Chemistry
J Biol Chem. 2013 July 12; 288(28): 20110.
PMCID: PMC3711278

Molecular Mechanism for Biomineralization in a Eukaryotic Single-celled Organism♦

Pentalysine Clusters Mediate Silica Targeting of Silaffins in Thalassiosira pseudonana

♦ See referenced article, J. Biol. Chem. 2013, 288, 20100–20109

Diatoms are single-celled eukaryotic microalgae that produce nanopatterned silica-based cell walls (biosilica). Biosilica is an organic-inorganic composite composed of several building blocks that are formed in specialized intracellular vesicles called silica deposition vesicles (SDVs). Silaffins are the predominant phosphoproteins in the biosilica's organic matrix and are believed to be important for the morphogenesis of the silica nanopatterns. In this Paper of the Week, a team led by Nils Kröger at Technische Universität Dresden in Germany used fluorescence microscopy and subcellular membrane fractionation to track the intracellular transport of the silaffin Sil3. They demonstrated that the complete transport of Sil3 and its incorporation into the biosilica relied on a lysine-rich motif that was 12–14 amino acids in length. The motif is conserved in all silaffins and is necessary for their proper trafficking. The authors say, “The results of the present work provide the first insight into the molecular mechanisms for biogenesis of mineral-forming vesicles from a eukaryotic organism.”

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Proposed pathways for intracellular transport of proteins associated with the diatom cell wall.

Articles from The Journal of Biological Chemistry are provided here courtesy of American Society for Biochemistry and Molecular Biology