Toward the three-dimensional structure of the Escherichia coli DNA-bindingprotein H-NS: A CD and fluorescence study

The DNA-binding protein H-NS compacts DNA and acts as a specific transcript ion factor regulating the expression of various bacterial genes, The small abundant protein binds to curved DNA without apparent sequence specificity and the exact nature of its DNA interaction is still unknown. H-NS lacks an y common DNA-binding or oligomerization motif and except for a C-terminal f ragment of the protein no high resolution structural information is availab le today, Since the complete structure of H-NS is of considerable interest for understanding its versatile regulatory features, and in lack of high-re solution data for the complete molecule, we have combined circular dichrois m (CD) and fluorescence measurements to collect secondary- and higher-order structural information on H-NS, Comparison of CD analyses of wild type H-N S and functional defective mutants allowed assigning secondary structure el ements to the N-terminal oligomerization domain of the protein. Moreover, a ccording to fluorescence energy-transfer data we calculate a 45 Angstrom di stance between the DNA-binding and the oligomerization domain of H-NS, (C) 2001 Academic Press.