(Below N is a link to NCBI taxonomic web page and E link to ESTHER at designed phylum.) > cellular organisms: NE > Eukaryota: NE > Amoebozoa: NE > Mycetozoa: NE > Dictyosteliida: NE > Dictyostelium: NE > Dictyostelium discoideum: NE
LegendThis sequence has been compared to family alignement (MSA) red => minority aminoacid blue => majority aminoacid color intensity => conservation rate title => sequence position(MSA position)aminoacid rate Catalytic site Catalytic site in the MSA MNKLLVFILLLLLLINISFARKRSYIKNTDASIVVTQFGAIKGIVEDTHR VFYGIPFAQPPVNQLRWENPIDLKPWENVRETLTQKSQCAQKCNLGPGVC SPIGTSEDCLYLDVFTPKDATPNSKYPVIVYIPGGAFSVGSGSVPLYDAT KFAQSSVIVVNINYRLGVLGFMGTDLMHGNYGFLDQIKALEWVYNNIGSF GGNKEMITIWGESAGAFSVSAHLTFTYSRQYFNAAISSSSPLTVGLKDKT TARGNANRFATNVGCNIEDLTCLRGKSMDEILDAQEKVGLTFGDKILDAF TIWSPVIDGDIIPMQPLTAVKEGKTYDVPTIIGNVKHEAIPFIYSFFQDS VGIDYYRVLVAIVFPLNAMKILPLYPAAPRGQDSRPILSELITDYLFRCP DRYHTVTNAKKLSSPTYHYHYVHVKSTGHSLDACDDKVCHGTELSLFFNS YELMGERLDNDEKELAIDINNYIVNFATTHNPNTGLSVPVQWRQVTSTQN STLILETTIETKDTFTNDPKCNALDLTYYRNQVRP
The genome of the lower eukaryote Dictyostelium discoideum comprises six chromosomes. Here we report the sequence of the largest, chromosome 2, which at 8 megabases (Mb) represents about 25% of the genome. Despite an A + T content of nearly 80%, the chromosome codes for 2,799 predicted protein coding genes and 73 transfer RNA genes. This gene density, about 1 gene per 2.6 kilobases (kb), is surpassed only by Saccharomyces cerevisiae (one per 2 kb) and is similar to that of Schizosaccharomyces pombe (one per 2.5 kb). If we assume that the other chromosomes have a similar gene density, we can expect around 11,000 genes in the D. discoideum genome. A significant number of the genes show higher similarities to genes of vertebrates than to those of other fully sequenced eukaryotes. This analysis strengthens the view that the evolutionary position of D. discoideum is located before the branching of metazoa and fungi but after the divergence of the plant kingdom, placing it close to the base of metazoan evolution.
Developing cells of Dictyostelium discoideum contain crystalline inclusion bodies. The interlattice spaces of the crystals are approximately 11 nm, and their edge dimensions vary in aggregating cells from 0.1 to 0.5 micron. The crystals are enclosed by a membrane with the characteristics of RER. To unravel the nature of the crystals we isolated them under electron microscopical control and purified the two major proteins that cofractionate with the crystals, one of an apparent molecular mass of 69 kD, the other of 56 kD. This latter protein proved to be identical with the protein encoded by the developmentally regulated D2 gene of D. discoideum, as shown by its reactivity with antibodies raised against the bacterially expressed product of a D2 fusion gene. The D2 gene is known to be strictly regulated at the transcript level and to be controlled by cAMP signals. Accordingly, very little of the 56-kD protein was detected in growth phase cells, maximal expression was observed at the aggregation stage, and the expression was stimulated by cAMP pulses. The 69-kD protein is the major constituent of the crystals and is therefore called "crystal protein." This protein is developmentally regulated and accumulates in aggregating cells similar to the D2 protein, but is not, or is only slightly regulated by cAMP pulses. mAbs specific for either the crystal protein or the D2 protein, labeled the intracellular crystals as demonstrated by the use of immunoelectron microscopy. The complete cDNA-derived amino acid sequence of the crystal protein indicates a hydrophobic leader and shows a high degree of sequence similarity with Torpedo acetylcholinesterase and rat lysophospholipase. Because the D2 protein also shows sequence similarities with various esterases, the vesicles filled with crystals of these proteins are named esterosomes.
