Cheregi Otilia, Miranda Hélder, Gröbner Gerhard, Funk Christiane
Dept. of Chemistry, Umeå University, 90187 Umeå, Sweden.
Dept. of Chemistry, Umeå University, 90187 Umeå, Sweden.
J Photochem Photobiol B. 2015 Nov;152(Pt B):383-94. doi: 10.1016/j.jphotobiol.2015.05.007. Epub 2015 May 22.
The serine type Deg/HtrA proteases are distributed in a wide range of organisms from Escherichia coli to humans. The cyanobacterium Synechocystis sp. PCC 6803 possesses three Deg protease orthologues: HtrA, HhoA and HhoB. Previously we compared Synechocystis 6803 wild type cells exposed to mild or severe stress conditions with a mutant lacking all three Deg proteases and demonstrated that stress had strong impact on the proteomes and metabolomes. To identify the biochemical processes, which this protease family is involved in, here we compared Synechocystis sp. PCC 6803 wild type cells with a mutant lacking all three Deg proteases grown under normal growth conditions (30°C and 40 μmol photons m(-2) s(-1)). Deletion of the Deg proteases lead to the down-regulation of proteins related to the biosynthesis of outer cell layers (e.g. the GDP mannose 4,6-dehydratase) and affected protein secretion. During the late growth phase of the culture Deg proteases were found to be secreted to the extracellular medium of the Synechocystis sp. PCC 6803 wild type strain. While cyanobacterial Deg proteases seem to act mainly in the periplasmic space, deletion of the three proteases influences the proteome and metabolome of the whole cell. Impairments in the outer cell layers of the triple mutant might explain the higher sensitivity toward light and oxidative stress, which was observed earlier by Barker and coworkers.
丝氨酸型Deg/HtrA蛋白酶广泛分布于从大肠杆菌到人类的多种生物体中。蓝藻集胞藻PCC 6803拥有三种Deg蛋白酶同源物：HtrA、HhoA和HhoB。此前，我们将暴露于轻度或重度胁迫条件下的集胞藻6803野生型细胞与缺乏所有三种Deg蛋白酶的突变体进行了比较，结果表明胁迫对蛋白质组和代谢组有强烈影响。为了确定这个蛋白酶家族参与的生化过程，我们在此将集胞藻PCC 6803野生型细胞与在正常生长条件（30°C和40 μmol光子m(-2) s(-1)）下生长的缺乏所有三种Deg蛋白酶的突变体进行了比较。Deg蛋白酶的缺失导致与外细胞层生物合成相关的蛋白质（如GDP甘露糖4,6-脱水酶）表达下调，并影响蛋白质分泌。在培养的生长后期，发现Deg蛋白酶被分泌到集胞藻PCC 6803野生型菌株的细胞外培养基中。虽然蓝藻Deg蛋白酶似乎主要在周质空间发挥作用，但三种蛋白酶的缺失会影响整个细胞的蛋白质组和代谢组。三重突变体在外细胞层的损伤可能解释了Barker及其同事之前观察到的对光和氧化胁迫更高的敏感性。
