A model for Fis N-terminus and Fis-invertase recognition

In this modeling, we show that the elusive Fis N-terminus involved in invertase-mediated site-specific DNA inversion is, by all indications, a hinged flapping loop. The prediction is based on a combined sequence and secondary structure alignment against known structures of protein segments, as well as a tetrapeptide fragment observed crystallographically. Its validity is strongly supported by the ability to interpret consistently the available mutagenesis data pertaining to this region including, especially, a series of deletion mutants which until this work had been a puzzle in the search for structural explanations. A model for Fis-invertase recognition is also proposed.