CHARACTERISTIC ANALYSIS OF THE LUXG GENE ENCODING THE PROBABLE FLAVINREDUCTASE THAT RESIDES IN THE LUX OPERON OF PHOTOBACTERIUM-LEIOGNATHI

Nucleotide sequence of the luxG gene (GenBank Accession No. AF053227) from Photobacterium leiognathi PL741 has been determined, and the enco ded probable flavin reductase is deduced. The probable flavin reductas e encoded by the luxG gene has a calculated M-r 26,544 and comprises 2 35 amino acid residues. The probable flavin reductase like the NAD(P)H -flavin reductase might catalyze the reduction of flavins. Alignment a nd comparison of the probable flavin reductases from P. leiognathi PL7 41, ATCC 25521, P. phosphoreum, Vibrio fischeri, and V. harveyi show t hat they are homologous; there is 66% homologous (29.4% identity and 3 6.6% similarity), Also, the probable flavin reductase is homologous to the NAD(P)H-flavin reductase; it is perceived that the probable flavi n reductase and the NAD(P)H-flavin reductase could be enzyme isoforms encoded by two genes of a multigene family for differential response f unctions. Functional analysis illustrates that the specific segment se quence lay inside and behind the luxG gene might form the potential ha irpin loops Omega gI, Omega gII, Omega o, and Omega oT as mRNA stabili ty loop or/and as the attenuator-like loop or the dynamic terminator-l ike block for sub-regulation in the lux operon. The gene order of the luxG gene in the lux operon and the lum operon is umQ-lumP-R&R-luxC-lu xD-luxA-luxB-luxN-luxE-luxG--> (R&R: regulatory region; ter: transcrip tional terminator), whereas the R&R is the regulatory region for the l um operon and the lux operon, and ter is the transcriptional terminato r for the lum operon. (C) 1998 Academic Press.