The three-dimensional structures of the protein called HetR from cyanobacterium Anabaena in complex with symmetric DNA were determined during this research project. This protein is required for controlling the nitrogen-fixing process for Cyanobacteria, which inhabit nearly all illuminated environments globally and play key roles in the carbon and nitrogen cycle of biosphere.

The structures of the protein-DNA complexes revealed several specific interactions between protein and DNA including a single glutamic acid in the protein directly contacting three successive cytosines in the DNA.  All known filamentous cyanobacteria contain the HetR protein as well as its regulatory palindromic DNA sequences consisting of three consecutive GC pairs.

This unique interaction between a protein factor and its DNA target is so important that it is common across all cyanobacteria from different environments around the world.

This research was published in the May Proceedings of the National Academy of Sciences.

Kim Y, Ye Z, Joachimiak G, Videau P, Young J, Hurd K, Callahan SM, Gornicki P, Zhao J, Haselkorn R, Joachimiak A. Structures of complexes comprised of Fischerella transcription factor HetR with Anabaena DNA targets. Proc Natl Acad Sci USA. 2013 May 7;110(19):E1716-23.