THE N-TERMINAL PART OF THE ESCHERICHIA-COLI DNA-BINDING PROTEIN FIS IS ESSENTIAL FOR STIMULATING SITE-SPECIFIC DNA INVERSION BUT IS NOT REQUIRED FOR SPECIFIC DNA-BINDING

FIS protein is involved in several different cellular processes stimulating site-specific recombination in phages Mu and lambda as well as transcription of stable RNA operons in E. coli. We have performed a mutational analysis of fis and provide genetic and biochemical evidence that a truncated version of FIS lacking the N-terminal region is sufficient for specific DNA binding and for stimulating lambda-excision. These mutants also retain their ability to autoregulate fis gene expression. Such mutant proteins, however, cannot stimulate the enhancer dependent DNA inversion reaction.