| Prenylation of a Rab1B mutant with altered GTPase activity is impaired in cell-free systems but not in intact mammalian cells. | |
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MedLine Citation:
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PMID: 8836150 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Previous studies have reached differing conclusions as to whether or not guanine-nucleotide-dependent conformational changes affect the ability of Rab proteins to undergo post-translational modification by Rab:geranylgeranyltransferase (Rab-GGTase). We now show that the ability of a Rab1B mutant [Q67L (Gln-67-->Leu)] with reduced intrinsic GTPase activity to undergo geranylgeranylation in cell-free assays depends on the guanine nucleotide composition of the system. When GTP is the predominant nucleotide in the assay, Rab1BQ67L is a poor substrate. However, when GDP is present and GTP is omitted, prenylation of the Q67L mutant is comparable with that of the wild-type (WT) protein. These studies, coupled with the poor prenylation of Rab1BWT in the presence of the non-hydrolysable GTP analogue guanosine 5'-[gamma-thio]triphosphate, support the notion that Rab-GGTase prefers substrates in the GDP conformation. When the abilities of Rab1BQ67L and Rab1BWT to undergo prenylation were compared by metabolic labelling of transiently expressed proteins in cultured human 293 cells, we did not observe a decline in prenylation of the mutant protein as predicted on the basis of the cell-free assays. Moreover, the Q67L mutant was comparable with the wild-type Rab1B in its ability to associate with co-expressed Rab GDP dissociation inhibitors in 293 cells. These findings raise the possibility that unidentified proteins present in intact cells may compensate for the reduced intrinsic GTPase activity of the Q67L mutant, allowing a significant proportion of the nascent Rab1BQ67L to assume a GDP conformation. The differential prenylation of Rab1BQ67L in cell-free systems versus intact cells underscores the importance of evaluating the post-translational modification of specific Rab mutants in vivo, where poorly characterized regulatory proteins may have a significant effect on GTPase activity or nucleotide exchange rates. |
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Authors:
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A L Wilson; K M Sheridan; R A Erdman; W A Maltese |
Publication Detail:
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Type: In Vitro; Journal Article; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: The Biochemical journal Volume: 318 ( Pt 3) ISSN: 0264-6021 ISO Abbreviation: Biochem. J. Publication Date: 1996 Sep |
Date Detail:
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Created Date: 1996-11-20 Completed Date: 1996-11-20 Revised Date: 2009-11-18 |
Medline Journal Info:
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Nlm Unique ID: 2984726R Medline TA: Biochem J Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 1007-14 Citation Subset: IM |
Affiliation:
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Weis Center for Research, Geisinger Clinic, Danville, PA 17822-2616, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Amino Acid Sequence Animals Base Sequence Cattle Cell Line Cell-Free System DNA Primers / genetics GTP Phosphohydrolases / genetics*, metabolism* GTP-Binding Proteins / genetics*, metabolism* Guanine Nucleotide Dissociation Inhibitors* Guanosine Diphosphate / metabolism Guanosine Triphosphate / metabolism Humans Mutagenesis, Site-Directed Point Mutation Protein Prenylation Rats Recombinant Proteins / genetics, metabolism Reticulocytes / metabolism rab1 GTP-Binding Proteins* |
| Grant Support | |
ID/Acronym/Agency:
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CA34569/CA/NCI NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/DNA Primers; 0/GDP dissociation inhibitor 1; 0/Guanine Nucleotide Dissociation Inhibitors; 0/Recombinant Proteins; 146-91-8/Guanosine Diphosphate; 86-01-1/Guanosine Triphosphate; EC 3.6.1.-/GTP Phosphohydrolases; EC 3.6.1.-/GTP-Binding Proteins; EC 3.6.1.-/RAB1B protein, rat; EC 3.6.5.2/rab1 GTP-Binding Proteins |
| Comments/Corrections | |
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