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首页> 外文期刊>Biochemistry >Evidence that the FX domain in photosystem I interacts with the subunit PsaC: site-directed changes in PsaB destabilize the subunit interaction in Chlamydomonas reinhardtii.
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Evidence that the FX domain in photosystem I interacts with the subunit PsaC: site-directed changes in PsaB destabilize the subunit interaction in Chlamydomonas reinhardtii.

机译：光系统I中的FX域与PsaC亚基相互作用的证据：PsaB中的定点变化破坏了莱茵衣藻中的亚基相互作用。

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摘要

The highly conserved amino acid sequence PCDGPGRGGTC in both photosystem I reaction center core proteins PsaA and PsaB has been predicted to contribute the four cysteine ligands for coordination of the 4Fe-4S iron-sulfur cluster FX, and we have proposed a working model for the binding of PsaC to this domain of the reaction center core heterodimer [Rodday et al. (1993) Photosynth. Res. 36, 1-9]. We have investigated structure-function relationships between this domain and the PsaC subunit by site-directed mutagenesis of the conserved prolines P560 and P564, and the charged residues D562 and R566 in the eucaryotic alga Chlamydomonas reinhardtii. The D562N and R566E mutants did not accumulate the PsaA and PsaB reaction center proteins, indicating that these residues are essential for the stable assembly of photosystem I. The P560A, P560L, and P564L mutants accumulated functional reaction centers but showed an impaired interaction between the reaction center core complex and the PsaC subunit. We observed that the reaction centers of the proline mutants dissociated more readily in urea, and reconstitution of the mutant core preparations using PsaC and Fe-S cluster insertion protocols in vitro were incomplete. We suggest that P560 and D562 contribute to the stability of the FX cluster, most likely by providing essential hydrogen bonding to the C561 ligand. The data obtained from the P564 and R566 replacements provide direct evidence that the intercysteinyl region in PsaB is a domain involved in the interaction between PsaC and the reaction center core.
机译：据预测，在光系统I反应中心核心蛋白PsaA和PsaB中，高度保守的氨基酸序列PCDGPGRGGTC会贡献四个半胱氨酸配体来协调4Fe-4S铁硫簇FX，并且我们提出了结合的工作模型PsaC到反应中心核心异二聚体的这个结构域[Rodday等。 （1993）光合作用。 Res。 36，1-9]。我们已经通过保守的脯氨酸P560和P564的定点诱变以及真核藻类衣藻衣藻中带电残基D562和R566的定点诱变研究了该结构域与PsaC亚基之间的结构-功能关系。 D562N和R566E突变体未积累PsaA和PsaB反应中心蛋白，表明这些残基对于光系统I的稳定装配是必不可少的。P560A，P560L和P564L突变体积累了功能性反应中心，但显示了反应之间的相互作用减弱中心核心复合体和PsaC亚基。我们观察到脯氨酸突变体的反应中心在尿素中更容易解离，并且体外使用PsaC和Fe-S簇插入方案对突变体核心制剂的重构不完整。我们认为，P560和D562最有可能通过提供与C561配体的必要氢键来促进FX簇的稳定性。从P564和R566置换获得的数据提供直接证据，证明PsaB中的半胱氨酸间区域是参与PsaC和反应中心核心之间相互作用的域。

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