Common structural features of the luxF protein and the subunits of bacterial luciferase: Evidence for a (βα)8 fold in luciferase

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Abstract
The amino acid sequence identity and potential structural similarity between the subunits of bacterial luciferase and the recently determined structure of the luxF molecule are examined. The unique β/α barrel fold found in luxF appears to be conserved in part in the luciferase subunits. From secondary structural predictions of both luciferase subunits, and from structural comparisons between the protein product of the luxF gene, NFP, and glycolate oxidase, we propose that it is feasible for both luciferase subunits to adopt a (βα)8 barrel fold with at least 2 excursions from the (βα)8 topology. Amino acids conserved between NFP and the luciferase subunits cluster together in 3 distinct “pockets” of NFP, which are located at hydrophobic interfaces between the β‐strands and α‐helices. Several tight turns joining the C‐termini of β‐strands and the N‐termini of α‐helices are found as key components of these conserved regions. Helix start and end points are easily demarcated in the luciferase subunit protein sequences; the N‐cap residues are the most strongly conserved structural features. A partial model of the luciferase β subunit from Photobacterium leiognathi has been built based on our crystallographically determined structure of luxF at 1.6 Å resolution.