Mechanism of stepwise electron transfer in six-transmembrane epithelial antigen of the prostate (STEAP) 1 and 2.
Mechanism of stepwise electron transfer in six-transmembrane epithelial antigen of the prostate (STEAP) 1 and 2.
复制标题
前列腺六跨膜上皮抗原（STEAP）中逐步电子转移的机制1和2。
作者：
Chen K;Wang L;Shen J;Tsai AL;Zhou M;Wu G
前列腺六跨膜上皮抗原（STEAP）1-4是膜包埋的血红素蛋白，其在跨膜结构域（TMD）中螯合血红素辅基。STEAP 2 -4，而不是STEAP 1，具有细胞内氧化还原酶结构域（OxRD），可以介导跨膜电子转移从NADPH通过FAD和血红素。然而，目前尚不清楚STEAP 1是否可以建立生理相关的电子转移链。在这里，我们表明，STEAP 1可以减少减少FAD或可溶性细胞色素b5还原酶，作为替代OxRD，提供了第一个证据，STEAP 1可以支持跨膜电子转移链。目前尚不清楚FAD是否始终与STEAP结合，它将电子从OxRD中的NADPH传递到TMD中的血红素。我们发现STEAP 2还原的FAD可以被STEAP 1利用，这表明FAD是可扩散的，而不是保持与STEAP 2结合。我们通过冷冻电子显微镜确定了与NADP+和FAD复合的人STEAP 2的结构，总分辨率为3.2 μ m，并发现这两种辅因子与STEAP 4类似地结合STEAP 2，这表明可扩散的FAD是STEAP中电子转移机制的一般特征。我们还证明了STEAP 2还原次氮基三乙酸铁（Fe 3 +-NTA）的速度明显慢于STEAP 1，并提出还原速度较慢是由于Fe 3 +-NTA与STEAP 2中高度柔性的胞外区结合较差。这些结果为理解STEAP的功能和机制奠定了坚实的基础。
Six transmembrane epithelial antigen of the prostate (STEAP) 1–4 are membrane-embedded hemoproteins that chelate a heme prosthetic group in a transmembrane domain (TMD). STEAP2–4, but not STEAP1, have an intracellular oxidoreductase domain (OxRD) and can mediate cross-membrane electron transfer from NADPH via FAD and heme. However, it is unknown whether STEAP1 can establish a physiologically relevant electron transfer chain. Here, we show that STEAP1 can be reduced by reduced FAD or soluble cytochrome b5 reductase that serves as a surrogate OxRD, providing the first evidence that STEAP1 can support a cross-membrane electron transfer chain. It is not clear whether FAD, which relays electrons from NADPH in OxRD to heme in TMD, remains constantly bound to the STEAPs. We found that FAD reduced by STEAP2 can be utilized by STEAP1, suggesting that FAD is diffusible rather than staying bound to STEAP2. We determined the structure of human STEAP2 in complex with NADP+ and FAD to an overall resolution of 3.2 Å by cryo-electron microscopy and found that the two cofactors bind STEAP2 similarly as in STEAP4, suggesting that a diffusible FAD is a general feature of the electron transfer mechanism in the STEAPs. We also demonstrated that STEAP2 reduces ferric nitrilotriacetic acid (Fe3+-NTA) significantly slower than STEAP1 and proposed that the slower reduction is due to the poor Fe3+-NTA binding to the highly flexible extracellular region in STEAP2. These results establish a solid foundation for understanding the function and mechanisms of the STEAPs.
前列腺1（STEAP1）的六跨膜上皮抗原具有单个B血红素，能够减少金属离子复合物和氧气。
影响因子：
2.9
作者：
Kim K;Mitra S;Wu G;Berka V;Song J;Yu Y;Poget S;Wang DN;Tsai AL;Zhou M
通讯作者：
Zhou M
影响因子：
5.9
作者：
通讯作者：
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