铁硫簇的生物合成

Biosynthesis of Iron-sulfur Cluster

铁硫簇在细胞的生物学过程中起着重要的作用,可参与电子传递、代谢控制和基因调节等过程。研究显示铁硫簇具有多样性,它的合成依赖于ISC和SUF系统,固氮酶中还需要NIF系统的参与。ISC系统由iscSUA-hscBA-fdx基因串编码,合成的是一类“管家”蛋白,适于在正常条件下表达。SUF系统由基因串sufABCDSE编码,常在恶劣环境如氧化应激和铁饥饿条件下表达。NIF系统由nifSU基因编码,适于固氮酶(厌氧条件下起作用)铁硫簇的合成。

Owing to the versatile electronic properties of iron and sulfur, iron-sulfur clusters are important in diverse biological processes, including electron transfer chains, metabolic pathways and gene regulatory circuits. Chemistry has revealed the great diversity of Fe-S clusters occurring in proteins. Biological studies showed Fe-S cluster biogenesis depends upon ISC and SUF systems, or a NIF system in nitrogenase. ISC system is encoded by a gene cluster iscSUA-hscBA-fdx, which can be transcribed to form 6 proteins named IscS, IscU, IscA, HscB, HscA and ferredoxin. SUF system is coded by a gene cluster sufABCDSE, which can be transcribed to form 6 proteins including a scaffold protein, a L-cysteine desulfurase, a sulfur acceptor and 3 components of an activator complex. It seems that ISC is the house-keeping one that functions under normal laboratory conditions, while the SUF system is required in harsh environmental conditions such as oxidative stress and iron starvation. NIF system is composed of two proteins nifS and nifU, which is encoded by nifiSU gene and take an important role in iron-sulfur cluster assembly of nitrogenase that is active in anaerobic condition.