Catalase-peroxidases of Legionella pneumophila:: Cloning of the katA gene and studies of KatA function
Catalase-peroxidases of Legionella pneumophila:: Cloning of the katA gene and studies of KatA function
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DOI：
10.1128/jb.182.23.6679-6686.2000
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发表时间：
2000-12-01
影响因子：
3.2
通讯作者：
Steinman, HM
中科院分区：
文献类型：
--
作者：
Bandyopadhyay, P;Steinman, HM
嗜肺军团菌是退伍军人肺炎的病原体，含有两种具有过氧化活性和过氧化活性的酶：KatA 和 KatB。为了解决高度同源的过氧化氢酶-过氧化物酶体内功能冗余、重叠或离散的问题，克隆了katA基因，并在嗜肺军团菌和大肠杆菌中研究了其功能，并与本实验室之前对katB的研究进行了比较。 katA 在指数生长过程中被诱导，是稳定期的主要过氧化物酶。当katA失活时，嗜肺军团菌对外源过氧化氢更敏感，并且在THP-1巨噬细胞系中毒性较低，与katB类似。 KatA 和 KatB 与不同过氧化共底物的过氧化氢活性相当，但 KatA 对联茴香胺的活性高出 Ave 倍。与这些冗余或重叠功能的例子相反，当katA失活时，稳定期存活率降低100至10,000倍，而katB无效时与野生型相比没有变化。理解这种离散的体内功能的主要线索是证明 KatA 是周质的，而 KatB 是细胞质的。这种稳定相表型表明，对过氧化氢敏感的靶标存在于稳定相的细胞质外，或者 KatA 的过氧化活性对于周质中的稳定相氧化还原反应（可能是二硫键的形成）至关重要。由于饥饿诱导的稳定期是嗜肺军团菌获得毒力的先决条件，因此对katA在稳定期的功能和调节的进一步研究可能有助于了解该病原体的感染机制。
Legionella pneumophila, the causative organism of Legionnaires' pneumonia, contains two enzymes with catalatic and peroxidatic activity, KatA and KatB. To address the issue of redundant, overlapping, or discrete in vivo functions of highly homologous catalase-peroxidases, the gene for katA was cloned and its function was studied in L. pneumophila and Escherichia coli and compared with prior studies of katB in this laboratory. katA is induced during exponential growth and is the predominant peroxidase in stationary phase. When katA is inactivated, L. pneumophila is more sensitive to exogenous hydrogen peroxide and less virulent in the THP-1 macrophage cell line, similar to katB. Catalatic-peroxidatic activity with different peroxidatic cosubstrates is comparable for KatA and KatB, hut KatA is Ave times more active towards dianisidine. In contrast with these examples of redundant or overlapping function, stationary-phase survival is decreased by 100- to 10,000-fold when katA is inactivated, while no change from wild type is seen for the katB null. The principal clue for understanding this discrete in vivo function was the demonstration that KatA is periplasmic and KatB is cytosolic. This stationary-phase phenotype suggests that targets sensitive to hydrogen peroxide are present outside the cytosol in stationary phase or that the peroxidatic activity of KatA is critical for stationary-phase redox reactions in the periplasm, perhaps disulfide bond formation. Since starvation-induced stationary phase is a prerequisite to acquisition of virulence by L. pneumophila, further studies on the function and regulation of katA in stationary phase may give insights on the mechanisms of infectivity of this pathogen.