ADP reduces the oxygen-binding affinity of a sensory histidine kinase, FixL: the possibility of an enhanced reciprocating kinase reaction.
ADP reduces the oxygen-binding affinity of a sensory histidine kinase, FixL: the possibility of an enhanced reciprocating kinase reaction.
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DOI：
10.1073/pnas.0305795101
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发表时间：
2004-03
影响因子：
11.1
通讯作者：
Hiro Nakamura;H. Kumita;K. Imai;T. Iizuka;Y. Shiro
中科院分区：
文献类型：
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作者：
Hiro Nakamura;H. Kumita;K. Imai;T. Iizuka;Y. Shiro
根瘤菌 FixL/FixJ 系统是基于血红素的氧传感器的范例，属于普遍存在的双组分信号转导系统。无氧（脱氧）FixL 通过使用 ATP 在不变的组氨酸残基处自磷酸化，并催化伴随的磷酰基转移至 FixJ，但氧与 FixL 血红素部分的结合会使激酶活性失活。在这里，我们证明 ADP 充当变构效应器，当 FixL 中的传感器结构域在激酶反应中由 ATP 产生时，会降低其与氧的结合亲和力。在存在 FixJ 的情况下，将 ADP 添加到纯化的野生型 FixL 溶液中会导致氧结合亲和力下降约 4 至 5 倍。相反，磷酸化缺陷突变体（其中激酶结构域保守的 ATP 结合催化位点受损）没有表现出这种变构效应。这一发现揭示了双组分组氨酸激酶同型二聚化的重要性； ADP 在同二聚体的一个亚基的磷酸化反应中产生，通过降低配体结合亲和力，增强另一个亚基的组氨酸激酶活性，类似于两缸往复式发动机。
The rhizobial FixL/FixJ system, a paradigm of heme-based oxygen sensors, belongs to the ubiquitous two-component signal transduction system. Oxygen-free (deoxy) FixL is autophosphorylated at an invariant histidine residue by using ATP and catalyzes the concomitant phosphoryl transfer to FixJ, but oxygen binding to the FixL heme moiety inactivates the kinase activity. Here we demonstrate that ADP acts as an allosteric effector, reducing the oxygen-binding affinity of the sensor domain in FixL when it is produced from ATP in the kinase reaction. The addition of ADP to a solution of purified wild-type FixL resulted in an approximately 4- to 5-fold decrease in oxygen-binding affinity in the presence of FixJ. In contrast, phosphorylation-deficient mutants, in which the well conserved ATP-binding catalytic site of the kinase domain is impaired, showed no such allosteric effect. This discovery casts light on the significance of homodimerization of two-component histidine kinases; ADP, generated in the phosphorylation reaction in one subunit of the homodimer, enhances the histidine kinase activity of the other, analogous to a two-cylinder reciprocating engine by reducing the ligand-binding affinity.