title: Biochemical Composition and Assembly of Biosilica-associated Insoluble Organic Matrices from the Diatom Thalassiosira pseudonana.
abstract: The nano- and micropatterned biosilica cell walls of diatoms are remarkable examples of biological morphogenesis and possess highly interesting material properties. Only recently has it been demonstrated that biosilica-associated organic structures with specific nanopatterns (termed insoluble organic matrices) are general components of diatom biosilica. The model diatom Thalassiosira pseudonana contains three types of insoluble organic matrices: chitin meshworks, organic microrings, and organic microplates, the latter being described in the present study for the first time. To date, little is known about the molecular composition, intracellular assembly, and biological functions of organic matrices. Here we have performed structural and functional analyses of the organic microrings and organic microplates from T. pseudonana. Proteomics analysis yielded seven proteins of unknown function (termed SiMat proteins) together with five known silica biomineralization proteins (four cingulins and one silaffin). The location of SiMat1-GFP in the insoluble organic microrings and the similarity of tyrosine- and lysine-rich functional domains identifies this protein as a new member of the cingulin protein family. Mass spectrometric analysis indicates that most of the lysine residues of cingulins and the other insoluble organic matrix proteins are post-translationally modified by short polyamine groups, which are known to enhance the silica formation activity of proteins. Studies with recombinant cingulins (rCinY2 and rCinW2) demonstrate that acidic conditions (pH 5.5) trigger the assembly of mixed cingulin aggregates that have silica formation activity. Our results suggest an important role for cingulins in the biogenesis of organic microrings and support the hypothesis that this type of insoluble organic matrix functions in biosilica morphogenesis.
authors.affiliation: From the B CUBE Center for Molecular Bioengineering and.
authors.forename: Alexander
authors.initials: A
authors.lastname: Kotzsch
authors.affiliation: From the B CUBE Center for Molecular Bioengineering and.
authors.forename: Damian
authors.initials: D
authors.lastname: Pawolski
authors.affiliation: the Max-Planck-Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany, and.
authors.forename: Alexander
authors.initials: A
authors.lastname: Milentyev
authors.affiliation: the Max-Planck-Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany, and.
authors.forename: Anna
authors.initials: A
authors.lastname: Shevchenko
authors.affiliation: the Max-Planck-Institute of Plant Physiology, 14476 Potsdam, Germany.
authors.forename: André
authors.initials: A
authors.lastname: Scheffel
authors.affiliation: From the B CUBE Center for Molecular Bioengineering and.
authors.forename: Nicole
authors.initials: N
authors.lastname: Poulsen
authors.affiliation: the Max-Planck-Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany, and.
authors.forename: Andrej
authors.initials: A
authors.lastname: Shevchenko
authors.affiliation: From the B CUBE Center for Molecular Bioengineering and the Department of Chemistry and Food Chemistry, Technische Universität Dresden, 01307 Dresden, Germany, kroeger@bcube-dresden.de.
authors.forename: Nils
authors.initials: N
authors.lastname: Kröger
mesh_terms: D002473:Cell Wall / Q000737:chemistry / Q000648:ultrastructure; D017377:Diatoms / Q000737:chemistry / Q000648:ultrastructure*; D005109:Extracellular Matrix / Q000737:chemistry / Q000378:metabolism*; D012822:Silicon Dioxide / Q000737:chemistry / Q000378:metabolism*
chemical_list: D012822:Silicon Dioxide
keywords: algae; biomineralization; cell wall; intrinsically disordered protein; morphogenesis; post-translational modification (PTM); protein self-assembly; proteomics