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. 2008 Jul;9(7):655-61.
doi: 10.1038/embor.2008.80. Epub 2008 May 30.

Crucial structural role for the PH and C1 domains of the Vav1 exchange factor

Jonathan Rapley  1 , Victor L J Tybulewicz, Katrin Rittinger
Affiliations

Crucial structural role for the PH and C1 domains of the Vav1 exchange factor

Jonathan Rapley et al. EMBO Rep. 2008 Jul.

Abstract

The Vav family of proteins are guanine nucleotide exchange factors (GEFs) for the Rho family of GTPases, which regulate various cellular functions, including T-cell activation. They contain a catalytic Dbl homology (DH) domain that is invariably followed by a pleckstrin homology (PH) domain, which is often required for catalytic activity. Vav proteins are the first GEFs for which an additional C1 domain is required for full biological activity. Here, we present the structure of a Vav1 fragment comprising the DH-PH-C1 domains bound to Rac1. This structure shows that the PH and C1 domains form a single structural unit that packs against the carboxy-terminal helix of the DH domain to stabilize its conformation and to promote nucleotide exchange. In contrast to previous reports, this structure shows that there are no direct contacts between the GTPase and C1 domain but instead suggests new mechanisms for the regulation of Vav1 activity.

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Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Figure 1
Figure 1
Overall structure of the Rac1–Vav1 DH–PH–C1 complex. (A) Diagram showing the domain structure of Vav1. The DH–PH–C1 fragment is shown in the same colours as used throughout the manuscript. The domain boundaries as determined by Prosite (http://www.expasy.ch/prosite/) are indicated. (B) Ribbon diagram of the Rac1–Vav1 DH–PH–C1 structure, with Rac1 coloured in grey, the DH domain in cyan, the PH domain in yellow and the C1 domain in orange. The two Zn2+ ions bound to the C1 domain are shown as grey spheres. Ac, acidic; CH, calponin homology; DH, Dbl homology; PH, pleckstrin homology.
Figure 2
Figure 2
The Rac1–Vav1 interaction and nucleotide exchange. (A) Detailed view of the interface between Asp 65 and Arg 66 in the switch II region of Rac1, and residues from helix α6 of the DH domain. Atoms are coloured by type except carbons, which are the same colour as in Fig 1B. The dashed lines indicate hydrogen bonds. Nucleotide exchange activity of (B) active (amino acids (aa) 189–575) and (C) autoinhibited (aa 170–575) Vav1 DH–PH–C1 and the isolated DH domain (aa 190–400) towards Rac1, Cdc42 and RhoA, as well as intrinsic exchange rates. DH, Dbl homology; PH, pleckstrin homology.
Figure 3
Figure 3
The DH–PH–C1 interface. Detailed view of the interface between residues from helix α6 of the DH domain and the PH and C1 domains. The positions of residues Gln 542, Tyr 544 and Lys 555 within the C1 domain that have been discussed in the text are indicated. DH, Dbl homology; PH, pleckstrin homology.
Figure 4
Figure 4
The C1 domain of Vav1. (A) Overlap of the C1 domain of Vav1 (orange) with that of the typical C1 domain of PKCδ bound to phorbol-13-acetate (1PTR, blue) and the atypical C1 domain of Raf1 (1FAR, green). The ligand bound to PKCδ is shown in a ball-and-stick representation. (B) Surface representation of the C1 domain of PKCδ with bound phorbol acetate. (C) Surface representation of Vav1 DH–PH–C1 shows a pocket in the C1 domain in the same position in which phorbol acetate is bound to PKCδ (shown for comparison). DH, Dbl homology; PH, pleckstrin homology; PKCδ, protein kinase Cδ.
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