Cnu is a nucleoid protein that has a high degree of sequence homology with Hha/YmoA familyproteins, which bind to chromatin and regulate the expression of
Escherichia coli virulence genes inresponse to changes in temperature or ionic strength. Here, we determined its solution structure and dynamicproperties and mapped H-NS binding sites. Cnu consists of three
helices that are comparable withthose of Hha, but it has significant flexibility in the C-terminal region and lacks a short
helix presentin Hha. Upon increasing ionic strength, the helical structure of Cnu is destabilized, especially at the endsof the helices. The dominant H-NS binding sites, located at helix 3 as in Hha, reveal a common structuralplatform for H-NS binding. Our results may provide structural and dynamic bases for the similarity anddissimilarity between Cnu and Hha functions.