title: Identification and isoprenylation of plant GTP-binding proteins.
abstract: To identify isoprenylated plant GTP-binding proteins, Arabidopsis thaliana and Nicotiana tabacum cDNA expression libraries were screened for cDNA-encoded proteins capable of binding [32P]GTP in vitro. ATGB2, an Arabidopsis homologue of the GTP-binding protein Rab2, was found to bind GTP in vitro and to be a substrate for a geranylgeranyl:protein transferase (GGTase) present in plant extracts. The carboxyl terminus of this protein contains a -GCCG sequence, which has not previously been shown to be recognized by any prenyl:protein transferase (PTase), but which most closely resembles that isoprenylated by the type II GGTase (-XXCC, -XCXC, or -CCXX). In vitro geranylgeranylation of an Arabidopsis Rab1 protein containing a carboxyl-terminal-CCGQ sequence confirmed the presence of a type II GGTase-like activity in plant extracts. Several other proteins were also identified by in vitro GTP binding, including Arabidopsis and tobacco homologues of Rab11, ARF (ADP-ribosylation factor) and Sar proteins, as well as a novel 22 kDa Arabidopsis protein (ATG81). This 22 kDa protein had consensus GTP-binding motifs and bound GTP with high specificity, but its structure was not closely related to that of any known GTP-binding protein (it most resembled proteins within the ARF/Sar and G protein alpha-subunit superfamilies).
authors.affiliation: Department of Biology, Indiana University-Purdue University at Indianapolis 46202-5132, USA.
authors.forename: B
authors.initials: B
authors.lastname: Biermann
authors.forename: S K
authors.initials: SK
authors.lastname: Randall
authors.forename: D N
authors.initials: DN
authors.lastname: Crowell
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004224:Diterpenes / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D015723:Gene Library; D006160:Guanosine Triphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D010947:Plants, Toxic; D017368:Protein Prenylation; D018749:RNA, Plant / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics; D014166:Transferases / Q000378:metabolism; D020693:rab2 GTP-Binding Protein
chemical_list: D018076:DNA, Complementary; D004224:Diterpenes; D010940:Plant Proteins; D018749:RNA, Plant; D006160:Guanosine Triphosphate; C017338:geranylgeraniol; D014166:Transferases; D019204:GTP-Binding Proteins; D020693:rab2 GTP-Binding Protein