The Streptomyces master regulator BldD binds c-di-GMP sequentially to create a functional BldD2-(c-di-GMP)4 complex.
Schumacher, M.A., Zeng, W., Findlay, K.C., Buttner, M.J., Brennan, R.G., Tschowri, N.(2017) Nucleic Acids Res 45: 6923-6933
- PubMed: 28449057 
- DOI: https://doi.org/10.1093/nar/gkx287
- Primary Citation of Related Structures:  
5TZD, 5TZF, 5TZG - PubMed Abstract: 
Streptomyces are ubiquitous soil bacteria that undergo a complex developmental transition coinciding with their production of antibiotics. This transition is controlled by binding of a novel tetrameric form of the second messenger, 3΄-5΄ cyclic diguanylic acid (c-di-GMP) to the master repressor, BldD. In all domains of life, nucleotide-based second messengers allow a rapid integration of external and internal signals into regulatory pathways that control cellular responses to changing conditions. c-di-GMP can assume alternative oligomeric states to effect different functions, binding to effector proteins as monomers, intercalated dimers or, uniquely in the case of BldD, as a tetramer. However, at physiological concentrations c-di-GMP is a monomer and little is known about how higher oligomeric complexes assemble on effector proteins and if intermediates in assembly pathways have regulatory significance. Here, we show that c-di-GMP binds BldD using an ordered, sequential mechanism and that BldD function necessitates the assembly of the BldD2-(c-di-GMP)4 complex.
Organizational Affiliation: 
Department of Biochemistry, Duke University School of Medicine, Durham, NC 27701, USA.