title: Possible role of ubiquitin in silica biomineralization in diatoms: identification of a homologue with high silica affinity.
abstract: In diatom silicon biomineralization peptides are believed to play a role in silica precipitation and the consequent structure direction of the cell wall. Characterization of such peptides should reveal the nature of this organic-inorganic interaction, knowledge that may eventually well be used to expand the existing range of artificial silicas ("biomimicking"). Biochemical studies on Navicula pelliculosa revealed a set of proteins, which have a high affinity for a solid silica matrix; some were only eluted from the matrix when SDS-denaturation was applied. One of the proteins with an affinity for silica, about 8.5 kDa, is shown to be a homologue of ubiquitin on the basis of its N-terminal amino acid sequence; ubiquitin itself is a highly conserved 8.6 kDa protein that is involved in protein degradation. This finding is in line with a model of silica biomineralization in diatoms that implies the removal of templating polypeptides when pores in the growing cell wall develop. Western blotting with specific anti-ubiquitin antibodies confirmed cross-reactivity. Immunocytochemical localization of ubiquitin indicates that it is present along the diatom cell wall and inside pores during different stages of valve formation.
authors.affiliation: Department of Marine Biology, Center for Ecological and Evolutionary Studies, University of Groningen, P.O. Box 14, 9750 AA Haren, The Netherlands. s.hazelaar@biol.rug.nl
authors.forename: Sandra
authors.initials: S
authors.lastname: Hazelaar
authors.forename: Han J
authors.initials: HJ
authors.lastname: van der Strate
authors.forename: Winfried W C
authors.initials: WW
authors.lastname: Gieskes
authors.forename: Engel G
authors.initials: EG
authors.lastname: Vrieling
mesh_terms: D040761:Biomimetic Materials / Q000737:chemistry / Q000378:metabolism; D002478:Cells, Cultured; D017377:Diatoms / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D006863:Hydrogen-Ion Concentration; D008903:Minerals / Q000737:chemistry / Q000378:metabolism; D008970:Molecular Weight; D011485:Protein Binding; D012822:Silicon Dioxide / Q000737:chemistry* / Q000378:metabolism*; D014018:Tissue Distribution; D025801:Ubiquitin / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D008903:Minerals; D025801:Ubiquitin; D012822:Silicon Dioxide