Proto-oncogene vav isoform 1, also known as VAV1, is a member of the VAV gene family. The VAV1 proteins are guanine nucleotide exchange factors (GEFs) for Rho family GTPases that activate pathways leading to actin cytoskeletal rearrangements and transcriptional alterations. In addition, VAV1 contains an SH2 domain, which could indicate its role as a substrate for tyrosine kinases. Expression of VAV1 is limited exclusively to cells of hematopoietic origin, including those of the erythroid, lymphoid and myeloid lineages. Recombinant human VAV1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.