Nucleotide sequence of theluzAgene (GenBank accession No. AF039303) fromPhotobacterium leiognathiATCC 25521 (NCIMB 2193) has been determined, and the chaperone encoded by theluzAgene was deduced. The LuzA chaperone has a calculated M r 26,295 and comprises 230 amino acid residues; the hydrophobic α-helix N-terminal 21 amino acid residues MKKTIFALLFMSVFI SYPSFA is the leader peptide, therefore the matured LuzA chaperone has a calculated M r 23,871 and comprises 209 amino acid residues only. The periplasmic LuzA chaperone is the protein concerned with the protein folding, assembly and stability. TheluzAgene and the related genes are closely linked to thesodgene, that encoding Cu/Zn superoxide dismutase enables to enhance bioluminescence of theluxoperon; the gene order of theluzAgene and related genes is -ufo'-luzA-ufoI-ufoII-ter->-R&R'-sod-ufo --->. In transcomplementation bioluminoassaysin vivoelicit that the LuzA chaperone might be not directly concerned with bioluminescence of theluxoperon fromP. leiognathiinE. coli, but might enable to stabilize the proteins related to bioluminescence. The unidentifiedufoIIgene closely linked to theluzAgene is able to enhance bioluminescence.