Structure of the GTPase-binding Domain of Sec5 and Elucidation of its Ral Binding Site

The exocyst complex is involved in the final stages of exocytosis, when vesicles are targeted to the plasma membrane and dock. The regulation of exocytosis is vital for a number of processes, for example, cell polarity, embryogenesis, and neuronal growth formation. Regulation of the exocyst complex...

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Bibliographic Details
Published in:The Journal of biological chemistry 2003-05, Vol.278 (19), p.17053-17059
Main Authors: Mott, Helen R., Nietlispach, Daniel, Hopkins, Louise J., Mirey, Gladys, Camonis, Jacques H., Owen, Darerca
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Binding Sites
Escherichia coli
GTP Phosphohydrolases - chemistry
GTP Phosphohydrolases - metabolism
Life Sciences
Membrane Proteins - analysis
Membrane Proteins - chemistry
Membrane Proteins - genetics
Membrane Proteins - metabolism
Mice
Molecular Sequence Data
Other
Protein Binding
Protein Conformation
Protein Structure, Tertiary
ral GTP-Binding Proteins - chemistry
ral GTP-Binding Proteins - metabolism
Sequence Alignment
Vesicular Transport Proteins
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Summary:The exocyst complex is involved in the final stages of exocytosis, when vesicles are targeted to the plasma membrane and dock. The regulation of exocytosis is vital for a number of processes, for example, cell polarity, embryogenesis, and neuronal growth formation. Regulation of the exocyst complex in mammals was recently shown to be dependent upon binding of the small G protein, Ral, to Sec5, a central component of the exocyst. This interaction is thought to be necessary for anchoring the exocyst to secretory vesicles. We have determined the structure of the Ral-binding domain of Sec5 and shown that it adopts a fold that has not been observed in a G protein effector before. This fold belongs to the immunoglobulin superfamily in a subclass known as IPT domains. We have mapped the Ral binding site on this domain and found that it overlaps with protein-protein interaction sites on other IPT domains but that it is completely different from the G protein-geranyl-geranyl interaction face of the Ig-like domain of the Rho guanine nucleotide dissociation inhibitor. This mapping, along with available site-directed mutagenesis data, allows us to predict how Ral and Sec5 may interact.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M300155200