title: Arabidopsis Rab Geranylgeranyltransferases Demonstrate Redundancy and Broad Substrate Specificity in Vitro.
abstract: Posttranslational lipid modifications mediate the membrane attachment of Rab GTPases, facilitating their function in regulating intracellular vesicular trafficking. In Arabidopsis, most Rab GTPases have two C-terminal cysteines and potentially can be double-geranylgeranylated by heterodimeric Rab geranylgeranyltransferases (Rab-GGTs). Genes encoding two putative α subunits and two putative β subunits of Rab-GGTs have been annotated in the Arabidopsis thaliana genome, but little is known about Rab-GGT activity in Arabidopsis. In this study, we demonstrate that four different heterodimers can be formed between putative Arabidopsis Rab-GGT α subunits RGTA1/RGTA2 and β subunits RGTB1/RGTB2, but only RGTA1·RGTB1 and RGTA1·RGTB2 exhibit bona fide Rab-GGT activity, and they are biochemically redundant in vitro. We hypothesize that RGTA2 function might be disrupted by a 12-amino acid insertion in a conserved motif. We present evidence that Arabidopsis Rab-GGTs may have preference for prenylation of C-terminal cysteines in particular positions. We also demonstrate that Arabidopsis Rab-GGTs can not only prenylate a great variety of Rab GTPases in the presence of Rab escort protein but, unlike Rab-GGT in yeast and mammals, can also prenylate certain non-Rab GTPases independently of Rab escort protein. Our findings may help to explain some of the phenotypes of Arabidopsis protein prenyltransferase mutants.
authors.affiliation: From the Department of Biology, Washington University, Saint Louis, Missouri 63130.
authors.forename: Wan
authors.initials: W
authors.lastname: Shi
authors.affiliation: the Donald Danforth Plant Science Center, Saint Louis, Missouri 63132, and.
authors.forename: Qin
authors.initials: Q
authors.lastname: Zeng
authors.affiliation: From the Department of Biology, Washington University, Saint Louis, Missouri 63130.
authors.forename: Barbara N
authors.initials: BN
authors.lastname: Kunkel
authors.affiliation: the Department of Biology, University of Louisville, Louisville, Kentucky 40292 mark.running@louisville.edu.
authors.forename: Mark P
authors.initials: MP
authors.lastname: Running
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D019883:Alkyl and Aryl Transferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016384:Consensus Sequence; D003545:Cysteine / Q000378:metabolism; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D017354:Point Mutation; D017368:Protein Prenylation; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D013379:Substrate Specificity; D020691:rab GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D029681:Arabidopsis Proteins; D007527:Isoenzymes; D021122:Protein Subunits; C513165:Rab escort protein, Arabidopsis; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D019883:Alkyl and Aryl Transferases; C075607:Rab geranylgeranyltransferase; D020691:rab GTP-Binding Proteins; D003545:Cysteine
keywords: Arabidopsis thaliana; Rab; Rab geranylgeranyltransferase; gene duplication; geranylgeranyl diphosphate; post-translational modification (PTM); protein isoprenylation; small GTPase