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首页> 外文期刊>Journal of bacteriology >Mutagenesis at Two Distinct Phosphate-Binding Sites Unravels Their Differential Roles in Regulation of Rubisco Activation and Catalysis
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Mutagenesis at Two Distinct Phosphate-Binding Sites Unravels Their Differential Roles in Regulation of Rubisco Activation and Catalysis

机译：在两个不同的磷酸结合位点诱变揭示了其在Rubisco活化和催化调节中的不同作用。

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Orthophosphate (Pi) has two antagonistic effects on ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), stimulation of activation and inhibition of catalysis by competition with the substrate RuBP. The enzyme binds Pi at three distinct sites, two within the catalytic site (where 1P and 5P of ribulose 1,5-bisphosphate [RuBP] bind), and the third at the latch site (a positively charged pocket involved in active-site closure during catalysis). We examined the role of the latch and 5P sites in regulation of Rubisco activation and catalysis by introducing specific mutations in the enzyme of the cyanobacterium Synechocystis sp. strain PCC 6803. Whereas mutations at both sites abolished the Pi-stimulated Rubisco activation, substitution of residues at the 5P site, but not at the latch site, affected the Pi inhibition of Rubisco catalysis. Although some of these mutations substantially reduced the catalytic turnover of Rubisco and increased the Km(RuBP), they had little to moderate effect on the rate of photosynthesis and no effect on photoautotrophic growth. These findings suggest that in cyanobacteria, Rubisco does not limit photosynthesis to the extent previously estimated. These results indicate that both the latch and 5P sites participate in regulation of Rubisco activation, whereas Pi binding only at the 5P site inhibits catalysis in a competitive manner.
机译：正磷酸盐（P i ）对1,5-双磷酸核糖羧化酶/加氧酶（Rubisco）具有两种拮抗作用，通过与底物RuBP竞争来刺激活化和抑制催化作用。该酶在三个不同的位点结合P i ，两个在催化位点（核糖1,5-双磷酸[RuBP]的1P和5P结合），第三个在闩锁位点（正带电的口袋参与催化过程中的活性位封闭）。通过在蓝细菌 Synechocystis sp的酶中引入特定突变，我们研究了闩锁和5P位点在Rubisco活化和催化调节中的作用。菌株PCC6803。尽管两个位点的突变都消除了P i 刺激的Rubisco活化，但5P位点而不是闩锁位点的残基取代影响了P i 抑制Rubisco催化。尽管这些突变中的一些突变显着降低了Rubisco的催化转换并增加了 K m （RuBP），但它们对光合作用的速率影响很小至中等，对光合作用的速率没有影响。光合自养生长。这些发现表明，在蓝细菌中，Rubisco不会将光合作用限制在先前估计的范围内。这些结果表明，闩锁位点和5P位点都参与了Rubisco活化的调节，而仅在5P位点上的P i 结合以竞争方式抑制了催化作用。

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