More decorative than wallpaper: Silica biomineralization in diatoms leads to intricate structures in the cell wall (see SEM image) and depends on structure‐directing templates formed by the electrostatically driven assembly of positively charged polyamine derivatives and polyanions. The title peptides are a family of biologically relevant polyanions present in diatom biosilica and composed mainly of serine phosphate and acidic amino acid residues.

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Abstract. The extracellular matrix (ECM) of Volvox contains insoluble fibrous layers that surround individual cells at a distance to form contiguous cellular compartments. Using immunological techniques, we identified a sulfated surface glycoprotein (SSG 185) as the monomeric precursor of this substructure within the ECM. The primary structure of the SSG 185 polypeptide chain has been derivod from eDNA and genomic DNA. A central domain of the protein, 80 amino acid residues long, consists almost exclusively of hydroxyproline residues. The chemical structure of the highly sulfated polysaccharide covalently attached to SSG 185 has been determined by permethylation analysis. As revealed by EM, SSG 185 is a rod-shaped molecule with a 21-nm-long polysaccharide strand protruding from its central region. The chemical nature of the cross-links between SSG 185 monomers is discussed.T HE green algae of the order Volvocales range in complexity from unicellular Chlamydomonas through colonial genera to multicellular organisms, with differentiated cells in the genus Volvox. The individual cells are surrounded by an extracellular matrix (ECM) ~ constructed of hydroxyproline-rich glycoproteins (Miller et al., 1974). The most conserved morphological feature of the Volvocalean ECM is an outer layer. In Ch/amydomonas, this region is composed of a number of glycoproteins in a distinctive crystalline lattice that can be disassembled by chaotropic agents and recrystallized in vitro (Roberts, 1974;Hills et al., 1975;Catt et al., 1978; Roberts et al., 1985;Goodenough et al., 1986;Goodenough and Heuser, 1988).The inner portion of the Chlamydomonas cell wall is a fibrous network insoluble in chaotropic agents Goodenough and Heuser, 1985). It is within the evolutionary derivatives of this substructure that diversification has occurred to convert a simple cell wall into an ECM of the multicellular Volvocales. In these genera the ECM internal to the boundary zone is organized in highly regular patterns into fibrous layers that underlie the crystalline layer, ensheath individual cells, and surround cells at a distance to form contiguous cellular compartments (for review, see Kirk et al., 1986). These cellular compartments exhibit a honeycomb-like organization.The organization of the ECM of higher Volvocales has been analyzed in detail at the light-and electron-microscopic level. Recently, all the known details of the ECM architecture in representative species of Volvox were reviewed and a 1. Abbreviations used in this paper: CZ 3, cellular zone 3; ECM, extracellular matrix; SSG 185, sulfated surface glycoprotein with apparent molecular mass 185 kD. system of nomenclature was proposed (Kirk et al., 1986). According to these proposals, the honeycomb-like cellular compartments are designated cellular zone 3 (CZ 3), schematically shown in Fig. 2 D. In this article, we analyze the molecular structure of the glycoprotein that is the biosynthetic precursor of the CZ 3 structure of the ECM of Volvox carteri. In a previous article, we have shown th...

The sex‐inducing pheromone of Volvox carteri is a glycoprotein that triggers development of males and females at a concentration below 10(−16) M. Evidence is presented for the existence of a novel mechanism of signal amplification operating within the extracellular matrix of this multicellular organism. A family of 70 kDa matrix glycoproteins denoted pherophorins bear a C‐terminal domain being homologous to the sex‐inducing pheromone. Under the influence of the pheromone, this domain is liberated by highly specific proteolysis.

ISG is a sulphated, extracellular glycoprotein synthesized for only a few minutes in inverting Volvox embryos and inverting sperm cell packets. This control operates at the level of transcription. ISG has been characterized by studies of protein chemistry and electron microscopy. The primary structure of ISG has been derived from genomic DNA and cDNA. ISG is composed of a globular and a rod‐shaped domain. The rod‐shaped domain represents a member of the extensin family with numerous repeats of Ser‐(Hyp)4–6 motifs. A synthetic decapeptide matching the C‐terminal sequence is able to disaggregate the organism into individual cells. Immunofluorescence microscopy localizes ISG within the boundary zone of the ECM.