Photosynthetic Oxygen Evolution Is Stabilized by Cytochrome c550 against Heat Inactivation in Synechococcus sp. PCC 7002
Photosynthetic Oxygen Evolution Is Stabilized by Cytochrome c550 against Heat Inactivation in Synechococcus sp. PCC 7002
复制标题
细胞色素 c550 可以稳定光合放氧，防止聚球藻热失活。
作者：
Y. Nishiyama;H. Hayashi;Tadashi Watanabe;N. Murata
我们研究了负责光合放氧的热稳定性的因素，通过检查类囊体膜从蓝藻聚球藻7002。我们发现，用0.1%Triton X-100处理类囊体膜导致放氧热稳定性显著降低，并且可以通过用Triton X-100提取的组分重构膜来恢复热稳定性。通过两个连续的层析步骤从Triton X-100提取物中纯化负责恢复热稳定性的蛋白质。纯化的蛋白质分子量为16 kD，具有低氧化还原电位的c型Cyt的分光光度特性。连二亚硫酸盐减去抗坏血酸盐的差异光谱显示在551 nm处的[α]带最大值。我们能够克隆和序列的基因编码这个细胞色素从聚球藻属PCC 7002，部分氨基末端氨基酸序列的基础上。推导的氨基酸序列显示，该基因产物由34个残基的转运肽和136个残基的成熟蛋白组成。成熟蛋白与Cyt c550同源，Cyt c550是一种低氧化还原电位的Cyt。因此，我们的研究结果表明，细胞色素c550极大地影响了析氧的热稳定性。
We investigated the factors responsible for the heat stability of photosynthetic oxygen evolution by examining thylakoid membranes from the cyanobacterium Synechococcus sp. PCC 7002. We found that treatment of the thylakoid membranes with 0.1% Triton X-100 resulted in a remarkable decrease in the heat stability of oxygen evolution, and that the heat stability could be restored by reconstituting the membranes with the components that had been extracted by Triton X-100. The protein responsible for the restoration of heat stability was purified from the Triton X-100 extract by two successive steps of chromatography. The purified protein had a molecular mass of 16 kD and exhibited the spectrophotometric properties of a c-type Cyt with a low redox potential. The dithionite-minus-ascorbate difference spectrum revealed an [alpha] band maximum at 551 nm. We were able to clone and sequence the gene encoding this Cyt from Synechococcus sp. PCC 7002, based on the partial amino-terminal amino acid sequence. The deduced amino acid sequence revealed a gene product consisting of a 34-residue transit peptide and a mature protein of 136 residues. The mature protein is homologous to Cyt c550, a Cyt with a low redox potential. Thus, our results indicate that Cyt c550 greatly affects the heat stability of oxygen evolution.