GvpE is the transcriptional activator of the gvp gene cluster involved in gas vesicle formation in Haloabacterium salinarum. A 20-nucleotide sequence is required for the GvpE-mediated activation of the two oppositely oriented gvp promoters, P ( A ) and P ( D ). This sequence is located adjacent to the TATA-box and the transcription factor-B-binding site BRE, suggesting an interaction between GvpE and proteins of the transcription initiation apparatus. Here, we analysed the interaction of GvpE with the five different TATA-box-binding proteins, TBP, of Hbt. salinarum PHH1. The His-tagged TbpA through TbpE proteins were produced in Escherichia coli, bound to Ni-NTA matrices and tested for interaction with GvpE by protein-protein affinity chromatography. All Tbp(His) proteins retained the two different GvpE proteins from lysates of Haloferax volcanii transformants expressing the respective gvpE reading frame in pJAS35. Also, both GvpE(His) proteins bound to Ni-NTA matrices retained TbpB, whereas the 20-kDa soluble gas vesicle protein GvpH(His) neither bound TbpB nor GvpE from the respective lysates of Hfx. volcanii. From these results, it appears that GvpE interacts with any TBP of Hbt. salinarum. This interaction might attract TBP and subsequently TFB and RNAP to the promoter and thus enhance transcription of the gvp gene cluster.