Purification of lumazine proteins from Photobacterium leiognathi and Photobacterium phosphoreum: bioluminescence properties

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Abstract
Bright strains of the marine bioluminescent bacterium P. leiognathi produce a lumazine protein in amounts comparable to that previously found in P. phosphoreum. New protocols are developed for the purification to homogeneity of the proteins from both species in yields up to 60%. In dimmer strains the amount of lumazine protein in extracts are less, and also there is an accompanying shift of the bioluminescence spectral maximum to longer wavelength, 492 nm. Both types of lumazine proteins have identical fluorescence spectra, with maxima at 475 nm, so it is suggested that, whereas lumazine protein is the major emitter in bright strains, there is a 2nd emitter also present with a fluorescence maximum at longer wavelength. The 2 species of lumazine protein has the same 276 nm/visible absorbance ratio, 2.2, but differ in visible maxima: P. phosphoreum, 417 nm; P. leiognathi, 420 nm. For the latter the bound lumazine has .epsilon.420 = 10,100 M-1 cm-1, practically the same as in free solution. The 2 lumazine proteins also differ quantitatively in their effect on the in vitro bioluminescence reaction, i.e., at blue shifting the bioluminescence spectrum or altering the kinetics. The P. phosphoreum lumazine protein is more effective with its homologous luciferase or with P. leiognathi luciferase than is the lumazine protein from P. leiognathi. These differences may have an electrostatic origin.

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