中国科学院物理研究所
北京凝聚态物理国家研究中心
SM6组供稿
第50期
2020年06月24日
蛋白质动态结构分子开关: 植物捕光天线实现高效捕光和光保护功能间切换的机理研究

  zhiwuguanghexitongjiyaozaiduoyunhuoyintiandiguangzhaotiaojianxiabaochigaoxiaobuguanghechuannengxiaolv,youyaozaizhengwuqiangguangchixuzhaoshexiabimianyouciyinfadeyanghuasunshangjiguangbaohu。zhiwudeguangbaohugongnengshijiangguoshengdejifanengyiredexingshihaosandiao。 zaiziranhuanjingzhong,taiyangguangdefuzhaoqiangdukeyizaiduanshijianneichengxianchushijibeidezhangluo。dangyundeyinyingzhebizhushouqiangguangfuzhaodeyepianhou,yepianhaihuijiangguangbaohuzhuangtaichixushufenzhongzhijiu,ranhoucaiqiehuandaobuguangzhuangtai。lilunjisuanbiaoming,youyuzhuangtaikaiguanqiehuandezhihouxiaoying,keyidaozhi20%deguangnengsunshi。2016nian,meiguokexuejiatongguoyichuanjiyingongcheng,huodekaiguanhuifusulvjiakuaidetubianzhu,faxianqijingguanghexiaolvbiyeshengxingzengjiayue15% (science, 2016,354,857)。

  neimeguanghexitongshiruhediaokongdanbaizhifenzikongjianjiegouyikuaisuxiangyinghuanjingguangzhaotiaojiandebianhua,shixiandiguangzhaotiaojianxiagaoxiaonengliangchuandijijiejin90%dedianhefenliliangzixiaolv、bingzaiqiangguangzhaotiaojianxiakuaisuqieduanchuannengtongdaojinruguangbaohuzhuangtaide?zheigewentikunraolekexuejiajinbangeshiji,duigaiwentidehuidabingchanmingqiweiguanjiliduiyufenziyuzhongyitigaonongzuowuchanliangjuyouzhongdadezhidaoyiyi。

  zhongguokexueyuanwuliyanjiusuo/beijingningjutaiwuliguojiayanjiuzhongxinruanwuzhiwulishiyanshiwengyuxiangketizu,shenzhenwanshiyanshiliangzishengwuxue、meiguomingnisudadaxuehuaxuexigaojialiketizuhegianlugi vegliajiaoshouhezuo,yingyongchaokuaishijianfenbianyingguangguangpujimaichongshengwen(t-jump)-namiaoshijianfenbianzhonghongwaishuntaiguangpujiehequanyuanzifenzidonglixuemonijiliangzihuaxuejisuan,shiyanyulilunmiqiepeihe,jieshilegaodengzhiwuguangxitongiizhuyaobuguangtianxiandanbaisesufuhewu(light harvesting complex ii,lhcii)sanjuti,zuoweidanbaizhifenzijiqi,shiruheshixiangaoxiaobuguangheguangbaohugongnengjiankeniqiehuandejili。gaiyanjiubiaoming,qiangguangzhaoshexiadejubushengwenheguangjieshuidaozhideguanghemonangqiangcesuandudezengjiasuochanshengdequdongli,zaiweimiaoshijianchiduneiyoudaolhciidanbaizhibiangouyundong,daozhibuguangsesuduiyehuangsu-yelvsujiandejulijianxiao,fashengyelvsujifataibeiyehuangsufenzicuimiedenengliangzhuanyiguocheng,youcijiangduoyudejifatainengliangyouxiaodizhuanhuanchengrenengerhaosandiao,congershixianleyougaoxiaobuguangdaojifatainenglianghaosanzhuangtaijiandekuaisuqiehuan。zheiyifenzijiqidezuoyongjilimiqieguanlianleguanghexitongwaibuhuanjingtiaojian(huanjingwendu,shuidezhengtengzuoyong,guanghemodeyingdu)、neibufenzicengcidongtaijiegoubianhua、yijizhiwubiaoguanxianxiangdeyinguoguanxi,jiejueleguanghetixiruhekenidishixianyoudiguangzhaotiaojianxiadegaoxiaobuguang/chuannenggongnengqiehuandaogaoguangzhaotiaojianxiadeguangbaohugongnengzheiyigehexinkexuewenti。

  gaiyanjiujieshi,jujitaidelhciisanjutideyingguangshoumingheqiangdushouwenduhesuandudiaokong,wendushenggaohuozhesuanduzengjiadounenggoudaozhixianzhudeyingguangcuimiexianxiang。tongguoyingguangshoumingfenxibiaoming,lhciicunzailiangzhonggouxiangti,jizhangshoumingdebuguanggouxiang(light-harvesting, h)heduanshoumingdenengliangcuimiegouxiangti(quenching, q)。lingwaixitongzaijiaogaodewenduxiatongchanghaicunzaibianxingdedanbaigouxiang(denatured, d)。yinerzaibianwenguochengzhong,xitongzhongcunzaisanzhonggouxiangti,jih、q hed。jieheyingguangshoumingheqiangdufenxi,keyiyangededaosanzhexiangduihanliangsuiwendudebianhuaguanxi。jieguobiaoming,cuimietaiqdehanliangsuiwendushenggaoerzengjia,zai55℃zuoyou,dadaozuidazhi (tu1)。lingwai,danbaiderewendingxingfenxibiaoming,lhciisanjutizai55℃yixiadejiegoubianhuajihushiwanquankenide。

满堂彩tu1. shengwencushilhciisanjutiyouchuannengzhuangtaidaojifanengcuimiezhuangtaidezhuanhuanshiyitu。

  随后应用自主研发的高精度脉冲升温—纳秒时间分辨中红外光谱仪(Rev. Sci. Instr. 2015,86,053105),结合变温傅里叶变换红外光谱,研究了LHCII三聚体在热胁迫下发生的结构变化,指认了囊腔侧处于部分亲水的310螺旋E(Helix E)的二级结构谱峰位置,并通过单点突变重组蛋白(S123G)进一步证实了对关键二级结构310螺旋结构E的光谱指认。实验表明温度升高与酸度增加都会促使囊体腔侧一段处于松弛状态的310螺旋E向结构更紧凑的α-螺旋转变。热胁迫下310螺旋E向α-螺旋转变的时间约1微秒,新生的α-螺旋向疏水内核区插入的时间约1.24微秒 (图2)。

图2. 脉冲升温—时间分辨中红外光谱及动力学(a,b)(上半图)。实验表明新生α-螺旋插膜过程的时间尺度为1.24 μs (b)。分子动力学模拟结果(下半图)。分子动力学模拟揭示升温过程中处于松弛状态的310螺旋结构(E.M1: Helix E in Mononomer 1,蓝色部分)和相邻单体中的一段无规卷曲结构(C-terminus in Mononomer 2,蓝色部分)会协同转变为α-螺旋(红色部分)。

  全原子分子动力学模拟结果表明,在升温过程中,蛋白质部分结构单元会发生失水作用,导致结构单元间的疏水作用增强,引起310满堂彩螺旋E和相邻的LHCII单体中的一段无规卷曲结构协同转变为α-螺旋,并引起α-螺旋E和D向疏水核内部插入运动,从而在原子尺度上阐释了脉冲升温—时间分辨中红外光谱观察到的蛋白质二级结构的变化。α-螺旋E和D插膜运动引起的别构效应驱动一对交叉排列的跨膜螺旋A和B发生剪切运动,导致附着于跨膜螺旋对上的叶绿素分子与相邻的叶黄素分子之间的间距随温度的升高或酸度的增加而变小。进一步通过量子化学计算,揭示叶黄素分子(LUT)暗态(S1态)和叶绿素a激发态电子态耦合强度在一定的温度范围内,也随温度升高而增强,导致叶绿素激发态的能量淬灭,并且能量淬灭主要发生在LUT-Chl612这一色素对上(图3)。

tu3. butongwenduxialhciisanjutizhongyehuangsufenzi1 (lut1)heyelvsufenzijiandianzitaiouheqiangduyijiyehuangsufenzidegouxiangniuqu。

  更为详细的图像是(图4),当310满堂彩螺旋E转变为α-螺旋后,触发螺旋E和D在类囊体腔侧的插膜运动,并分别以螺旋D端的残基L206与螺旋B末端残基V80、L84构成剪叉内侧作用力的支点,以螺旋E端的残基W97与螺旋A在类囊体腔侧剪叉的末端残基F194、F195构成另一作用力的支点。类囊体腔侧的螺旋E与D在热能或酸度的驱动下形成一对顶杠,以螺旋A、B交叉点处的盐桥(Arg70-Glu180, Glu65-Arg185)为铰点,分别从跨膜螺旋A与B交叉面内侧将剪叉式排列的螺旋顶开,导致剪叉角度增加,带动两个剪叉式排列的叶黄素分子做相应的开叉运动,缩短了叶黄素分子与相邻的叶绿素分子之间的距离,增强了色素对间电子态的耦合,提升了叶绿素激发态能量的淬灭效率。尤其在低温条件下,位于腔侧的谷氨酸(E94)与螺旋E近端的赖氨酸K99形成氢键,随着温度的升高,螺旋E逐渐朝中心靠近,E94-K99之间的相互作用减弱,而E94与处于螺旋E中段的谷酰胺Q103形成新的氢键,这说明E94协同参与了螺旋E的插膜过程。上述模型与分子生物学中单点突变的实验结果相符合,如将E94突变成电中性甘氨酸,会导致叶绿素荧光淬灭效率降低。可见E94恰如开关中的触臂,K99及Q103分别为两个触点,当E94与K99相触的时候,系统处于高效捕光态,而当E94与Q103相触的时候,则处于光保护状态。

tu4. renengjisuanduqudonglhciisanjutifenzikaiguanjianchashiyundonggongzuoyuanli(zuo)jijianchashishengjiangjigou(you)leibishiyitu。

满堂彩  kejian,lhciiqiarujianchashishengjiangjiyiyangdefenzikaiguan (tu4),zairenenghuosuanduyoudaodeshushuizuoyongxia,chufaluoxuaneyudxiangshushuineihedechamoyundong,jiangdonglifenbiechuanjijianchadeliangbeiluoxuanayub,yinqixiangjianchashishengjiangjiyiyangdeyundong,poshiyehuangsufenzihexianglindeyelvsufenzixianghujiejin,congershixianyelvsujifataidenengliangcuimie。congfenzijiqidejiaodukedechuyixiasangetuilun:

满堂彩  (1)chamoyundongsulvshinengliangcuimieguochengdesulvjuedingbuzhou,shijianchiduwei1.24weimiao,yinciguanghexitongnenglianghaosanyeyinggaizaizheigeshijianchidu。wenxianbaodaodeshiyanjieguobiaoming,huotiyepiannenglianghaosandeshijianchiduwei1.4weimiao。

  (2)congjixiedejiaodukaolv,qiangceluoxuanchamozuoyongxuyaojingguojidaohuanjiedechuandicainenggoudaozhuanbianweikuamoluoxuandejianchashengjiangyundong,erchuandiguochengzhongshejidejixiedanyuanshidianxingderuanwuzhi,yinerguanghemogangduyueda,lidechuandixiaolvyuegao,nenglianghaosandexiaoguoyejiuyuehao,zheidianyeweiyizhishiyanshishisuozhengshi。

  (3)nengliangcuimietaiduiyingdeshijiaochakuamoluoxuanduidingjiaogengweizhangkaidezhuangtai,yinerchuyuguangbaohuzhuangtaideguanghemoyingdangbianbo(tu4,zuo),zheiyidianyeyuwenxianbaodaoshiyanguancexiangfu。

满堂彩  shangshufenzijizhibujinyuqijinbaodaodezhongduoshengwuxueshiyanguancexiangfu,haijieshilezhiwushiruheyingyongwentaiwenduheshuntaiwendulaishixiangaoxiaonenglianghaosan、tongshiyoukeyibimiandanbaizhirebianxingde。yibanqingkuangxia,danghuanjingwenduwei25℃shi,yepiandewendukeda40℃。yepianduijifanengdehaosanchiyushijianwei10weimiaoliangji,jinyibugusuan10weimiaoneixishoudeguangzishuquanbubianchengreliangkeyiyinqilhciisantishuntaiwendushangsheng14℃,bingqiegaishuntaiwenduchixushijianyuanxiaoyu100weimiaodedanbaizhikaishibianxingdetiaojian,yincibuhuiyinruewaidedanbaizhibianxing。cishichuyunenglianghaosanzhuangtaideshuntaiwendudadao54℃,zhenghaochuyunengliangcuimiedezuijiawendufujin,erdanbaizhidewendingxingzeyouwentaiwendu40℃jueding。kejianziranjieliyonggaoshuntaiwendushixianzuiyouhuanengliangcuimie,tongshiweichijiaodideyepianwentaiwenduyibaozhengdanbaizhijiegoudewanquankenixing。

满堂彩  gaixianggongzuoyi“dynamical and allosteric regulation of photoprotection in light harvesting complex ii”weitizaixianfabiaoyuscience china chemistry. (https://doi.org/10.1007/s11426-020-9771-2)。zhongkeyuanwulisuoboshishenglihaoheshenzhenwanshiyanshifuyanjiuyuanwangyingjieweilunwendebingliediyizuozhe,wengyuxianghegaojialiweigongtongtongxunlianxiren。

  gaiyanjiudedaoleguojiazirankexuejijinweizhongdianxiangmu(21433014)hezhongguokexueyuankeyanyiqishebeiyanzhixiangmu(yz200842,yjkyyq20170046)dezhichi。fenzidonglixuemonigongzuofenbiededaoleguojiaziranjijinwei、kejibuzhongdianyanfajihuagaoxingnengjisuanzhuanxianghemeiguonihdezizhu。

原文链接:
https://link.springer.com/article/10.1007/s11426-020-9771-2
满堂彩 DOI: https://doi.org/10.1007/s11426-020-9771-2