MBF1 (multiprotein bridging factor 1) is a highly conserved protein in archaea and eukaryotes. It was originally identified as a mediator of the eukaryotic transcription regulator BmFTZ-F1 (Bombyx mori regulator of fushi tarazu). MBF1 was demonstrated to enhance transcription by forming a bridge between distinct regulatory DNA-binding proteins and the TATA-box-binding protein. MBF1 consists of two parts: a C-terminal part that contains a highly conserved helix–turn–helix, and an N-terminal part that shows a clear divergence: in eukaryotes, it is a weakly conserved flexible domain, whereas, in archaea, it is a conserved zinc-ribbon domain.
1. K. Takemaru, F. Q. Li, H. Ueda, S. Hirose, Multiprotein bridging factor 1 (MBF1) is an evolutionarily conserved transcriptional coactivator that connects a regulatory factor and TATA element-binding protein. Proc Natl Acad Sci U S A 94, 7251 (1997).
2. de Koning, F. Blombach, H. Wu, S. J. Brouns, J. van der Oost, Role of multiprotein bridging factor 1 in archaea: bridging the domains? Biochem Soc Trans 37, 52 (2009).