Abstract
The Rab5 GTPase, an essential regulator of endocytosis and endosome biogenesis, is activated by guanine-nucleotide exchange factors (GEFs) that contain a Vps9 domain. Here, we show that the catalytic core of the Rab GEF Rabex-5 has a tandem architecture consisting of a Vps9 domain stabilized by an indispensable helical bundle. A family-wide analysis of Rab specificity demonstrates high selectivity for Rab5 subfamily GTPases. Conserved exchange determinants map to a common surface of the Vps9 domain, which recognizes invariant aromatic residues in the switch regions of Rab GTPases and selects for the Rab5 subfamily by requiring a small nonacidic residue preceding a critical phenylalanine in the switch I region. These and other observations reveal unexpected similarity with the Arf exchange site in the Sec7 domain.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence / physiology
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Animals
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Carrier Proteins / genetics
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Carrier Proteins / metabolism
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Catalytic Domain / physiology
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Endocytosis / physiology*
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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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Humans
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Intracellular Signaling Peptides and Proteins*
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Models, Molecular
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Molecular Sequence Data
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Mutation / genetics
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Phenylalanine / chemistry
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Protein Binding / physiology*
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Protein Structure, Secondary / physiology
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Sequence Homology, Amino Acid
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rab GTP-Binding Proteins / genetics
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rab GTP-Binding Proteins / metabolism
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rab5 GTP-Binding Proteins / metabolism*
Substances
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ALS2 protein, human
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Carrier Proteins
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Guanine Nucleotide Exchange Factors
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Intracellular Signaling Peptides and Proteins
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RABGEF1 protein, human
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RIN1 protein, human
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Phenylalanine
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rab GTP-Binding Proteins
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rab5 GTP-Binding Proteins