STUDY ON THE FUNCTIONAL SITES OF Mg~(2+) -INDUCED Chl α FLUORESCENCE AND SURFACE CHARGE CHANGES OF THYLAKOID MEMBRANES

Thylakoid polypeptide components, Mg~(2+) -induced Chl a fluorescence at 77K and surface chargechanges were measured to investigate the functional sites of Mg~(2+) in the regulation of energy distri-bution between two photosystems in completely and incompletely developed barley chloroplasts. It wasfound that in contrast to the completely developed chloroplasts, the incompletely developed chloroplastslacked Chl b and did not contain the 23KDa and 25KDa polypeptide components of LHC-PSII. In themeantime, these membranes did nor present Mg~(2+) -induced Cbl a fluorescence and surface charge changesof thylakoids. These results provided strong evidence that the 23KDa and 25KDa polypeptides ofLHC-PSII are the specific acting sites of the cation that induced these two phenomena. It is suggested in this paper that Mg~(2+) -induced change of excitation energy distribution betweentwo photosystems is produced by the mechanism due to electrostatic neutralization of LHC-PSII bythe cation to cause a structural or con     

刺松藻类囊体膜23kD和24kD多肽在阳离子调节激发能分配中的作用

与高等植物不同,Mg~(2+)诱导刺松藻类囊体膜Chla荧光F_(687)增高与其诱导膜表面电荷密度减小无平行相关性,用Ca~(2+)提去膜表面的30和31kD多肽(Q_B蛋白),对Mg~(2+)诱导上述两种效应无明显的影响,但用胰酶消化进一步除去膜表面的23和24kD多肽后,Mg~(2+)诱导F_(687)增高的效应随之消失,而诱导膜表面电荷密度变化的性质不变,这些结果证明,刺松藻类囊体膜表面的23和24kD多肽是Mg~(2+)诱导荧光变化的功能部位;Mg~(2+)诱导激发能分配的改变不受膜表面静电性质控制。     

关于光合膜上蛋白质的功能分析

本文用胰蛋白酶作探针研究了菠菜叶绿体膜结构与功能之间的关系.在胰蛋白酶消化过的叶绿体中,观察到低浓度的CCCP(10μM)对放O₂和电子传递速度有强烈的抑制作用.胰蛋白酶诱导的这类CCCP的抑制作用,可被牛血清蛋白所“阻滞”.牛血清蛋白可使胰蛋白酶消化引起的叶绿体光还原DCIP的抑制得到恢复,但对酶消化产生的放O₂抑制无恢复效果. 根据上述结果推论:在PS-Ⅱ膜上可能存在有类似“通道”和“门”的结构;囊状体膜上的蛋白质组分有微区域的差异.     

EFFECTS OF TRYPSIN ON PHOTOSYSTEM Ⅱ,ELECTRON TRANSPORT AND ENERGY DISTRIBUTION

The effects of trypsin on the light-induced variable fluorescence of both the normaland tris-washed spinach chloroplasts have been investigated and it is discovered that: (i)Trypsin clearly inhibits in both cases the light-induced variable fluorescence emissions;but when the exogenous electron donor SMC B is added, this inhibitroy effects of trypsinare greatly alleviated and the recovery efficiency is similar in both cases. (ii) In thepresence of DCMU, trypsin still inhibits the variable fluorescence intensity but theexogenous electron acceptor such as DCIP or Fecy has no influence on it. Based on the above results, the following conclusion can be drawn: trypsin can evident-ly inactivate the electron transport on the oxidizing side of PS-Ⅱ, which exists between thewater splitting enzyme system and SMCB binding site. However, the water splitting enzymeis not sensitive to trypsin. It might be assumed that there is some protein on the thylakoidmembrane that acts as regulator to the functional mechanism of     

FUNCTIONAL ANALYSIS OF PROTEINS ON THE THYLAKOID MEMBRANE——EFFECTS OF Mg~(2+) AND BSA ON THE TRYPSIN-INDUCED CHLOROPHYLL a FLUORESCENCE AND THYLAKOID MEMBRANE SURFACE CHARGE CHANGES IN SPINACH CHLOROPLASTS

Trypsin digestion of spinach chloroplasts not only inhibits light-induced variable fluorescence yield (△F/F_0) but also abolishes Mg~(2+) stimulating effect on △F/F_0. If chloroplasts are incubated by Mg~(2+) prior to trypsin digestion, Mg~(2+) stimulating ability remains unchanged whereas the enzyme-induced △F/F_0 decline itself is not affected. The protective effect of pretreatment of chloroplasts with Mg~(2+) against trypsin closely correlated with alteration of the net negative charge on the outer surface of the thylakoid membrane by Mg~(2+). In contrast to this, addition of BSA to the chloroplast digested with trypsin significantly recovers the light-induced variable fluorescence yield but it does not influence Mg~(2+)-induced variable fluorescence change. The recovery effect of BSA incubation is not dependent upon Mg~(2+) concentration. Also, BSA does not alter the net negative charge on the outer surface of the thylakoid membrane.These results demonstrate the existence of two independent prote     

THE FUNCTIONAL ROLE OF 23 kD AND 24 kD POLYPEPTIDES OF THYLAKOID IN Mg~(2+)-INDUCED CHANGE OF EXCITATION ENERGY DISTRIBUTION BETWEEN TWO PHOTOSYSTEMS IN THE CHLOROPLASTS FROM Codium fragile

In contrast to the chloroplasts from higher plants, Mg~(2+)-induced PS--Ⅱ fluorescence inten-sity increase does not relate to Mg~(2+)-induced surface charge density decrease of thylakoidin the chloroplasts from Codium fragile. Tbe extraction of the green alga chloroplasts withCa~(2+) to remove the 30--31kD polypeptide (Q_B protein) on the thylakoid surface does notaffect the above Mg~(2+)-induced phenomena. If the Ca~(2+)-treated chloroplasts are further di-gested by trypsin to remove the 23kD and 24kD polypeptides on the membrane surface,the Mg~(2+)-induced fluorescence effect will completely disappear whereas the property ofMg~(2+)-induced surface charge density changes remains unchanged. These results not onlyshow that the 23kDa and 24kDa polypeptides on the thylakoid surface are the specific act-ing sites of the cation that induce Chla fluorescence change, but also demonstrate that thecation-induced change of excitation energy distribution between two photosystems is not con-trolled by the electros     

关于光合膜上蛋白质的功能分析——Mg~(2 )和BSA对胰酶诱导菠菜叶绿体Chla荧光及膜表面电荷变化的影响

本文证明了胰酶消化菠菜叶绿体不仅抑制Chl的可变荧光产率(△F/F_o),而且使Mg~(2 )对△F/F_o的刺激效应消失。在酶消化前加Mg~(2 )与叶绿体进行预保温,对Mg~(2 )刺激△F/F_o的效应有保护作用,但对酶诱导△F/F_o下降本身无影响。这种保护作用与Mg~(2 )诱导类囊体膜表面电荷的改变密切相关。相反,在酶消化过的叶绿体中加入BS保温,对酶诱导的△F/F_o下降有明显的恢复作用,但对酶诱导Mg~(2 )刺激△F/F_o能力的消失无影响。这种恢复作用不因Mg~(2 )冲的存在而改变;BSA对膜表面电荷亦无任何影响。这些结果证明,光合膜表面可能存在有两类蛋白质或多肽,它们通过不同的机制调节激发能在两个光系统之间的分配与传递。     

胰蛋白酶对光系统Ⅱ电子传递和能量分配的影响

本文测定了胰蛋白酶对正常的和经Tris洗过的菠菜叶绿体光诱导可变荧光的影响,发现:(1)酶消化对这两种叶绿体的可变荧光产率有明显的抑制作用;加入PS—Ⅱ电子供体SMCB可使抑制作用显著减轻,其荧光的恢复效率在两种叶绿体中接近相等.(2)在有DCMU存在下,酶诱导的上述抑制作用仍很显著,且不受外加受体的影响. 由上述结果得出结论:胰蛋白酶对PS—Ⅱ氧化侧有明显的钝化作用,钝化的部位在水裂解酶系统与SMCB插入的位置之间,而水裂解酶系统本身对酶消化不敏感;光合膜上可能有某种控制激发能转移和分配的蛋白质存在.     

关于Mg~(2+)诱导Chla荧光及类囊体膜表面电荷变化的功能部位的探讨

本文用发育完全的和发育不完全的大麦叶绿体膜观察了它们的类囊体膜多肽成分、Mg~(2+)诱导Chla低温荧光及膜表面电荷的变化。发现发育不完全的叶绿体膜与发育完全的叶绿体膜不同,它们的类囊体膜缺少Chlb,不含LHC-PSII的23KDa和25KDa多肽成分,亦无Mg~(2+)诱导Chla荧光及膜表面电荷变化的效应。这些试验结果证明,LHC-PSII的23KDa和25KDa多肽系Mg~(2+)诱导这两种相关效应的功能部位。文中讨论了Mg~(2+)对LHC-PSII的静电中和作用而引起膜结构或构型的改变,可能是阳离子诱导激发能在两个光系统之间分配改变的重要原因。