title: A new member of the GP138 multigene family implicated in cell interactions in Dictyostelium discoideum.
abstract: The cellular slime mold Dictyostelium discoideum reproduces sexually under submerged and dark conditions. Its mating system is polymorphic and particularly interesting with respect to mechanisms of cell recognition. The cell-surface glycoprotein gp138 has been implicated in sexual cell interactions, as it was identified as a target molecule for the antibodies that block sexual cell fusion in D. discoideum. Two mutually homologous genes, GP138A and GP138B, have been cloned, but gene disruption experiments to clarify their functional relationships suggested that there is at least one more gene for gp138. Further protein analysis including peptide mapping also revealed that gp138 exists as three isoforms, DdFRP1, DdFRP2, and DdFRP3. GP138A encodes DdFRP2 and GP138B, DdFRP3, and the presence of a third gp138 gene encoding DdFRP1 was suggested. Here, we isolated and characterized a third GP138 gene, GP138C. Although the deduced amino acid sequences of GP138C matched completely with those of peptide fragments of DdFRP1 in the N-terminal half, the rest did not give complete matches. Overexpression of GP138C caused an increase in the intensity of DdFRP1, but disruption of this gene did not diminish DdFRP1. Our results indicate that GP138C encodes a protein very similar to but distinct from DdFRP1. The GP138 multigene family is thus composed of more members than previously expected, and their functional relationships are of special interest.
authors.affiliation: Institute of Biological Sciences, University of Tsukuba, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Hata
authors.forename: N
authors.initials: N
authors.lastname: Yamaguchi
authors.forename: Y
authors.initials: Y
authors.lastname: Tanaka
authors.forename: H
authors.initials: H
authors.lastname: Urushihara
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004023:Dictyostelium / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D005810:Multigene Family; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014170:Transformation, Genetic
chemical_list: D008562:Membrane Glycoproteins; C042344:glycoprotein GP138