Abstract
GDP-bound prenylated Rabs, sequestered by GDI (GDP dissociation inhibitor) in the cytosol, are delivered to destined sub-cellular compartment and subsequently activated by GEFs (guanine nucleotide exchange factors) catalysing GDP-to-GTP exchange. The dissociation of GDI from Rabs is believed to require a GDF (GDI displacement factor). Only two RabGDFs, human PRA-1 and Legionella pneumophila SidM/DrrA, have been identified so far and the molecular mechanism of GDF is elusive. Here, we present the structure of a SidM/DrrA fragment possessing dual GEF and GDF activity in complex with Rab1. SidM/DrrA reconfigures the Switch regions of the GTPase domain of Rab1, as eukaryotic GEFs do toward cognate Rabs. Structure-based mutational analyses show that the surface of SidM/DrrA, catalysing nucleotide exchange, is involved in GDI1 displacement from prenylated Rab1:GDP. In comparison with an eukaryotic GEF TRAPP I, this bacterial GEF/GDF exhibits high binding affinity for Rab1 with GDP retained at the active site, which appears as the key feature for the GDF activity of the protein.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Bacterial Proteins / chemistry*
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism*
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DNA-Binding Proteins / chemistry*
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism
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Guanine Nucleotide Dissociation Inhibitors / metabolism*
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Guanine Nucleotide Exchange Factors / chemistry*
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Guanine Nucleotide Exchange Factors / genetics
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Guanine Nucleotide Exchange Factors / metabolism*
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Guanosine Diphosphate / metabolism
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Guanosine Triphosphate / metabolism
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Humans
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Legionella pneumophila / metabolism*
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Legionnaires' Disease / metabolism*
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Liposomes / metabolism
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Magnesium / metabolism
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Models, Molecular
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Molecular Sequence Data
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Point Mutation
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Protein Binding
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Protein Conformation
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Sequence Alignment
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Substrate Specificity
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rab1 GTP-Binding Proteins / metabolism*
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rho-Specific Guanine Nucleotide Dissociation Inhibitors
Substances
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Bacterial Proteins
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DNA-Binding Proteins
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DrrA protein, Bacteria
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Guanine Nucleotide Dissociation Inhibitors
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Guanine Nucleotide Exchange Factors
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Liposomes
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SidM protein, Legionella pneumophila
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rho-Specific Guanine Nucleotide Dissociation Inhibitors
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Guanosine Diphosphate
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Guanosine Triphosphate
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rab1 GTP-Binding Proteins
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Magnesium