Kasai S
Department of Bioapplied Chemistry, Faculty of Engineering, Osaka City University, Sumiyoshi-ku, Osaka, 558-8585, Japan.
J Biochem. 1999 Aug;126(2):307-12. doi: 10.1093/oxfordjournals.jbchem.a022450.
In previous studies involving Photobacterium species we proposed that (i) P-flavin is the product of luciferase, (ii) the physiological function of the lux operon is not to produce light but to produce FP(390) (luxF protein), including its prosthetic group, P-flavin, and (iii) FP(390) reactivates oxidatively inactivated cobalamin-dependent methionine synthase similar to flavodoxin but at relatively high ionic strength. It seems difficult to extend this idea to all luminous bacteria because the luxF gene is not present in the lux operon in Vibrio or Xenorhabdus. But we predicted that a luciferase fragment which binds P-flavin should function like FP(390) in these species. In this study, we isolated P-flavin binding protein from Vibrio fischeri ATCC 7744. The obtained protein was a modified luciferase as expected, in which the beta-subunit was intact but about 25 amino acid residues at the C-terminus of the alpha-subunit were deleted and the prosthetic group was the fully reduced P-flavin. These results strongly support that the physiological function of the lux operon is as described above even in luminous bacteria other than Photobacterium species. We propose that chromophore B reported by Tu and Hastings [Tu, S.-C. and Hastings, J.W. (1975) Biochemistry 14, 1975-1980] is the reduced P-flavin.
在之前涉及发光杆菌属物种的研究中，我们提出：（i）黄素磷光体是荧光素酶的产物；（ii）lux操纵子的生理功能不是产生光，而是产生FP(390)（luxF蛋白），包括其辅基黄素磷光体；（iii）FP(390)能以类似于黄素氧还蛋白的方式在相对高离子强度下使氧化失活的钴胺素依赖性甲硫氨酸合酶重新激活。将这一观点推广到所有发光细菌似乎很困难，因为在弧菌属或嗜线虫致病杆菌属中，luxF基因并不存在于lux操纵子中。但我们预测，在这些物种中，结合黄素磷光体的荧光素酶片段应具有与FP(390)类似的功能。在本研究中，我们从费氏弧菌ATCC 7744中分离出了黄素磷光体结合蛋白。所获得的蛋白正如预期的那样是一种修饰的荧光素酶，其中β亚基完整，但α亚基C末端约25个氨基酸残基缺失，且辅基为完全还原态的黄素磷光体。这些结果有力地支持了即使在发光杆菌属物种以外的发光细菌中，lux操纵子的生理功能也是如上所述。我们提出，Tu和Hastings [Tu, S.-C. and Hastings, J.W. (1975) Biochemistry 14, 1975 - 1980]报道的发色团B就是还原态的黄素磷光体。
