10月5日，J. Biol. Chem.在線發(fā)表了生化與細(xì)胞所王恩多研究組研究論文：血紅素結(jié)合人細(xì)胞質(zhì)精氨酰-tRNA合成酶并抑制其催化活力,。
人細(xì)胞質(zhì)精氨酰-tRNA合成酶(hcArgRS)催化tRNAArg氨基?；葾rg-tRNAArg。Arg-tRNAArg一方面是蛋白質(zhì)生物合成的原料,，參與蛋白質(zhì)合成,；另一方面它也是精氨酰-tRNA：蛋白質(zhì)轉(zhuǎn)移酶的底物，轉(zhuǎn)移精氨?；降鞍踪|(zhì)的N-末端,，參與依賴泛素化的“N-末端規(guī)則”蛋白質(zhì)降解途徑。哺乳動(dòng)物細(xì)胞的ArgRS即參與蛋白質(zhì)生物合成,，又參與蛋白質(zhì)的降解,，如何調(diào)節(jié)ArgRS的這兩個(gè)相反的功能是非常重要的科學(xué)問(wèn)題。血紅素作為信號(hào)分子,，參與到許多重要的生命活動(dòng)中,，其中“N-末端規(guī)則”途徑就是一個(gè)血紅素的感應(yīng)器。
王恩多實(shí)驗(yàn)室的楊芳博士研究了血紅素與hcArgRS在體外的相互作用,，研究結(jié)果表明血紅素能夠以hcArgRS的Cys-115 作為特異性的軸向配體與之結(jié)合,，血紅素通過(guò)抑制hcArgRS的第一步反應(yīng)—氨基酸活化反應(yīng)，而抑制酶的tRNA精氨?；盍?。血紅素誘導(dǎo)hcArgRS的寡聚化是其抑制該酶催化活力的主要原因。氨基酰-tRNA合成酶家族是一個(gè)功能多樣的蛋白質(zhì)家族,，該研究對(duì)進(jìn)一步深入探索哺乳動(dòng)物ArgRS新的生物學(xué)功能提供了極有價(jià)值的線索,。
該研究工作得到科技部重大科學(xué)研究計(jì)劃，中國(guó)博士后基金,，上海市博士后基金,，中科院王寬誠(chéng)博士后基金以及上海生科院博士后基金的經(jīng)費(fèi)資助。(生物谷Bioon.com)
生物谷推薦英文摘要：
JBC doi: 10.1074/jbc.M110.159913
Hemin binds to human cytoplasmic arginyl-tRNA synthetase and inhibits its catalytic activity
Fang Yang, Xian Xia, Hui-Yan Lei and En-Duo Wang*
The free form of human cytoplasmic arginyl-tRNA synthetase (hcArgRS) is hypothesized to participate in ubiquitin-dependent protein degradation by offering arginyl-tRNAArg to arginyl-tRNA transferase (ATE1). We investigated the effect of hemin on hcArgRS based on the fact that hemin regulates several critical proteins in "N-end rule"protein degradation pathway. Extensive biochemical evidence has established that hemin could bind to both forms of hcArgRS in vitro. Based on the spectral changes of the Soret band on site-directed protein mutants, we identified Cys-115 as a specific axial ligand of hemin binding that is located in the Add1 domain. Hemin inhibited the catalytic activity of full-length and N-terminal 72-amino acid truncated hcArgRSs by blocking amino acid activation. Kinetic analysis demonstrated that the Km values for tRNAArg, arginine and ATP in the presence of hemin were not altered, but kcat values dramatically decreased compared with those in the absence of hemin. By comparison, the activity of prokaryotic ArgRS was not affected obviously by hemin. Gel filtration chromatography suggested that hemin induced oligomerization of both the isolated Add1 domain and the wild type enzyme, which could account for the inhibition of catalytic activity. However, the catalytic activity of a hcArgRS mutant with Cys-115 replaced by alanine (hcArgRS-C115A) was also inhibited by hemin, suggesting that hemin binding to Cys-115 is not responsible for the inhibition of enzymatic activity and that the specific binding may participate in other biological functions.
