MOLECULAR-CLONING AND CHARACTERIZATION OF GPA1, A G-PROTEIN ALPHA-SUBUNIT GENE FROM ARABIDOPSIS-THALIANA

We have isolated a gene coding for a G protein α subunit from the flowering plant Arabidopsis thaliana. This gene, named GPA1, was isolated by using a DNA probe generated by polymerase chain reaction based on protein sequences from mammalian and yeast G protein α subunits. The sequences of genomic and cDNA clones indicate that GPA1 has 14 exons, and the deduced amino acid sequence shows that the GPA1 gene product (GPα1) has 383 amino acid residues (44,582 Da). The GPα1 protein exhibits similarity to all known G protein α subunits - 36% of its amino acids are identical and 73% are similar (identical and conservative changes) to mammalian inhibitory guanine nucleotide-binding regulatory factor α subunits and transducins. Furthermore, the GPα1 protein has all of the consensus regions for a GTP-binding protein. The GPA1-encoded mRNA of 1.55 kilobases is most abundant in vegetative plant tissues, as determined by RNA blot analysis. Restriction fragment length polymorphism mapping experiments show that GPA1 is ≃ 1.2 centimorgans from the visible marker er on chromosome 2.