Spalten, a protein containing Galpha-protein-like and PP2C domains, is essential for cell-type differentiation in Dictyostelium.
We have identified a novel gene, Spalten (Spn) that is essential for Dictyostelium multicellular development. Spn encodes a protein with an amino-terminal domain that shows very high homology to Galpha-protein subunits, a highly charged inter-region, and a carboxy-terminal domain that encodes a functional PP2C. Spn is essential for development past the mound stage, being required cell autonomously for prestalk gene expression and nonautonomously for prespore cell differentiation. Mutational analysis demonstrates that the PP2C domain is the Spn effector domain and is essential for Spn function, whereas the Galpha-like domain is required for membrane targeting and regulation of Spn function. Moreover, Spn carrying mutations in the Galpha-like domain that do not affect membrane targeting but affect specificity of guanine nucleotide binding in known GTP-binding proteins are unable to fully complement the spn- phenotype, suggesting that the Galpha-like domain regulates Spn function either directly or indirectly by mediating its interactions with other proteins. Our results suggest that Spn encodes a signaling molecule with a novel Galpha-like regulatory domain.
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Department of Biology, Center for Molecular Genetics, University of California, San Diego (UCSD), La Jolla, California 92093-0634, USA. rafirtel@ucsd.edu
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D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002454:Cell Differentiation / Q000235:genetics*; D002462:Cell Membrane / Q000378:metabolism; D016384:Consensus Sequence; D004023:Dictyostelium / Q000166:cytology* / Q000235:genetics / Q000254:growth & development; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D005800:Genes, Fungal; D017125:Genes, Protozoan; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010749:Phosphoprotein Phosphatases / Q000737:chemistry; D010766:Phosphorylation; D011487:Protein Conformation; D054648:Protein Phosphatase 2; D000071636:Protein Phosphatase 2C; D011499:Protein Processing, Post-Translational; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013329:Structure-Activity Relationship
D005656:Fungal Proteins; D015800:Protozoan Proteins; C112495:SPNA protein, Dictyostelium discoideum; D029701:Saccharomyces cerevisiae Proteins; C087358:PTC1 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D000071636:Protein Phosphatase 2C; D019204:GTP-Binding Proteins