The lumazine protein-encoding gene in Photobacterium leiognathi is linked to the lux operon

The nucleotide (nt) sequence of the lumP (EMBL accession No. X65612) gene of Photobacterium leiognathi PL741 was determined and the amino acid (aa) sequence deduced. The encoded aa sequence of lumP was identified as that of the lumazine protein (LumP) by homology with that of Photobacterium phosphoreum (56%). This small protein has a calculated M(r) of 19,997 and comprises 186 aa residues. Biochemical studies suggested that LumP is the protein which, when combined with luciferase, is responsible for the bioluminescent spectrum shift from blue-green light (490-505 nm) to blue (470 nm) in P. leiognathi. The nt sequence of the flanking region showed that lumP is linked to the lux operon but runs in the opposite direction. The gene order of the lumP and lux operon is as follows: <--lumP-R&R-luxC-luxD-luxA-luxB-luxN-lu xE-->; the R&R regulatory region sequence included two promoter systems, PR for the lux operon and PL for the lumP or the lum operon.