Covalent structure of subunits of bacterial luciferase: NH2-terminal sequence demonstrates subunit homology.

The heterodimeric subunit structure of bacterial luciferase was demonstrated more than 10 years ago. The enzymes from both Beneckea harveyi and Photobacterium fischeri have since been studied in detail; they each consist of two nonidentical subunits, designated alpha and beta. Both are required for bioluminescence activity, with the active center apparently confined to the alpha subunit. Amino acid sequence analysis of the NH2 termini of the alpha and beta subunits of the B. harveyi and P. fischeri luciferases not only confirms the earlier observation that the alpha subunits are homologous but also demonstrates that the NH2-terminal sequences of the beta subunits of the luciferases from the two genera are homologous. Furthermore, within each luciferase, the NH2-terminal sequences of the alpha and beta subunits are similar, suggesting the possibility that the genes coding, for alpha and beta may have arisen by gene duplication, presumably prior to divergence of the lines leading to present-day luminous bacteria.