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You may include any references to papers as in: the use of JSmol in Proteopedia ^[1] or to the article describing Jmol ^[2] to the rescue.

Function

Vav1 is a Guanine Exchange Factor (GEF) for the Rho/Rac protein family ^[3]. It is involved in cellular response to external stimuli, by inducing cytoskeletal rearrangement or by inter-mediating pathways cascades. As such, the proto-oncogene encoded Vav1 protein has a role in growth and division of the cell, but also in apoptotic pathways. Vav1 is mainly found in hematopoietic cells ^[4] and is involved in the differentiation of T lymphocytes, then in B and T cells development and maturation ^[5]. Vav1 also has a role in Ca2+ induced signalling pathways in immune response of B and T cells. HIV-1 Nef protein has been found to bind specifically to Vav1, affecting its nucleus-to-cytoplasm distribution, and thus delaying the immune reaction ^[6]

Disease

Relevance

Structural highlights

The Vav1 are (from N ter to C ter): a calponin-homology (CH) domain, an acidic (Ac) domain, a DBL-homology (DH) domain also known as a rhoGEF domain, a pleckstrin-homology (PH) domain, a phorbol esters/diacylglycerol binding (C1) domain also called Zinc-finger domain and Src-homology (SH) 3 and 2 domains. ^{[7] [8]}

(residues 1 - 119): When the CH domain is deleted, Vav has a phosphorylation-independant GEF activity. Studies on Vav3 implies that CH plays a role in auto-inhibition of Vav via its interactions with the (between the residue 49 in CH and 181 in Ac), DH and regions (C1 interacts with L101 and L104 of CH). The contacts with DH and C1 seem passively driven by the interactions between Ac and CH, though. ^[9]

(residues 134 - 187): contains the Tyrosine (Y174) which activates Vav when phosphorylated. ^[10]

(residues 194 - 373): present in every Rho/rac GEF, it is the active site of the GTP exchange with the C1 domain in Vav. It always has a PH domain just after its C terminal.^[11]

(residues 402 - 504): point mutation in it don't change the exchange activity of Vav, so it isn't directly involved in its GEF function ^[12]. But the presence of phosphatidylinositol-4,5-bisphosphate (PIP 2) inhibits 90% of Vav activity while phosphatidylinositol-3,4,5-trisphosphate doubles it. It is very likely that the interactions between these lipids and Vav happen on the PH domain, as it is commonly the case on other proteins with this region. It should be noted that the activation of Vav is made in parallel of the one of PI3-kinase in TCR and BCR pathway. ^[13]

phorbol esters/diacylglycerol binding (C1) domain :