COMMON STRUCTURAL FEATURES OF THE LUXF PROTEIN AND THE SUBUNITS OF BACTERIAL LUCIFERASE - EVIDENCE FOR A (BETA-ALPHA)(8) FOLD IN LUCIFERASE

The amino acid sequence identity and potential structural similarity b etween the subunits of bacterial luciferase and the recently determine d structure of the luxF molecule are examined. The unique beta/alpha b arrel fold found in luxF appears to be conserved in part in the lucife rase subunits. From secondary structural predictions of both luciferas e subunits, and from structural comparisons between the protein produc t of the luxF gene, NFP, and glycolate oxidase, we propose that it is feasible for both luciferase subunits to adopt a (beta alpha)(8) barre l fold with at least 2 excursions from the (beta alpha)(8) topology. A mino acids conserved between NFP and the luciferase subunits cluster t ogether in 3 distinct ''pockets'' of NFP, which are located at hydroph obic interfaces between the beta-stands and alpha-helices. Several tig ht turns joining the C-termini of beta-strands and the N-termini of al pha-helices are found as key components of these conserved regions. He lix start and end points are easily demarcated in the luciferase subun it protein sequences; the N-cap residues are the most strongly conserv ed structural features. A partial model of the luciferase beta subunit from Photobacterium leiognathi has been built based on our crystallog raphically determined structure of luxF at 1.6 Angstrom resolution.