Murine extracellular superoxide dismutase is converted into the inactive fold by the Ser195Cys mutation.
Murine extracellular superoxide dismutase is converted into the inactive fold by the Ser195Cys mutation.
复制标题
小鼠细胞外超氧化物歧化酶通过 Ser195Cys 突变转化为失活折叠。
DOI：
10.1021/bi400171b
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发表时间：
2013
期刊：
影响因子：
2.9
通讯作者：
Enghild,JanJ
中科院分区：
文献类型：
--
作者：
Scavenius,Carsten;Petersen,JaneS;Thomsen,LineR;Poulsen,EbbeToftgaard;Valnickova-Hansen,Zuzana;Bowler,RussellP;Oury,TimD;Petersen,SteenV;Enghild,JanJ
We have previously shown that human extracellular superoxide dismutase (EC-SOD) exists as two variants with differences in their disulfide bridge patterns: one form is the active enzyme (aEC-SOD), and the other is inactive (iEC-SOD). The availability of both active and inactive folding variants significantly reduces the specific activity of EC-SODin vivo. Both forms are produced during biosynthesis, but the underlying folding mechanisms remain unclear. To address this issue, we expressed EC-SOD in heterologous systems that do not endogenously express iEC-SOD. Rodents express only aEC-SOD because they lack Cys195 (human EC-SOD sequence numbering), which is essential for the formation of iEC-SOD. However, cultured hamster cells and transgenic mice expressing human EC-SOD were able to produce both human a- and iEC-SOD variants, which led us to hypothesize that the folding was sequence-dependent rather than a property of the expression system. To substantiate this hypothesis, we expressed murine EC-SOD in a human cell line, and as expected, only aEC-SOD was produced. Significantly, when Cys195 was introduced, both murine aEC-SOD and a novel murine iEC-SOD were generated, and the specific activity of the murine EC-SOD was significantly reduced by the mutation. Collectively, these data suggest that Cys195 actuates the formation of iEC-SOD, independent of the expression system or host. In addition, the dual-folding pathway most likely requires biosynthesis factors that are common to both humans and rodents.
