Prosser J, Graham L, Maier R J
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218.
J Bacteriol. 1988 Apr;170(4):1990-3. doi: 10.1128/jb.170.4.1990-1993.1988.
Azotobacter vinelandii cultures express more H2 uptake hydrogenase activity when fixing N2 than when provided with fixed N. Hydrogen, a product of the nitrogenase reaction, is at least partly responsible for this increase. The addition of H2 to NH4+-grown wild-type cultures caused increased whole-cell H2 uptake activity, methylene blue-dependent H2 uptake activity of membranes, and accumulation of hydrogenase protein (large subunit as detected immunologically) in membranes. Both rifampin and chloramphenicol inhibited the H2-mediated enhancement of hydrogenase synthesis. Nif- A. vinelandii mutants with deletions or insertions in the nif genes responded to added H2 by increasing the amount of both whole-cell and membrane-bound hydrogenase activities. Nif- mutant strain CA11 contained fourfold more hydrogenase protein when incubated in N-free medium with H2 than when incubated in the same medium containing Ar. N2-fixing wild-type cultures that produce H2 did not increase hydrogenase protein levels in response to added H2.
与提供固定氮时相比，棕色固氮菌培养物在固定氮气时表现出更高的氢气摄取氢化酶活性。氮气还原酶反应的产物氢气至少部分导致了这种增加。向以NH4+培养的野生型培养物中添加氢气，导致全细胞氢气摄取活性增加、膜的亚甲基蓝依赖性氢气摄取活性增加以及膜中氢化酶蛋白（通过免疫学检测的大亚基）积累。利福平和平氯霉素均抑制氢气介导的氢化酶合成增强。在nif基因中存在缺失或插入的棕色固氮菌Nif-突变体，通过增加全细胞和膜结合氢化酶活性的量来响应添加的氢气。Nif-突变菌株CA11在无氮培养基中与氢气一起培养时，其氢化酶蛋白含量比在含有氩气的相同培养基中培养时多四倍。产生氢气的固氮野生型培养物不会因添加氢气而增加氢化酶蛋白水平。
