生物膜结构研究的一些进展

膜蛋白三维结构的解析存在很多困难.最近几年由于一些通道(如K⁺通道,Cl^-通道,水通道Aquaporin 1等)和泵（如Ca^2＋泵）的结晶获得成功,这些膜蛋白具有原子分辨率三维结构的解析才得以完成,从而基本阐明一些极性分子和离子选择性通过生物膜的分子机理.在膜脂结构方面,动物细胞质膜膜脂的分布是不均匀的.近年来已多方面证明,质膜具有一些被命名为“脂筏（lipid rafts）”和“质膜微囊（Caveolae）”的微区.它们富含鞘脂和胆固醇。简单介绍了这些脂质微区的大小、组分以及动态变化.根据研究结果,这类脂质微区含有大量信号分子,很可能具有信号传递中心的作用.此外,对脂筏在膜运送过程中的作用也进行一些评述.     

宗师百岁耕耘不息--热烈庆贺贝时璋教授百岁大寿

2003年10月10日,是我国卓越的生物学家贝时璋院士从事科研教学八十周年暨百岁华诞的大喜日子。 贝时璋教授学识渊博,治学严谨,师表千秋,桃李满园,是我国生物学界一位德高望重、广泛受人尊敬的杰出科学家、教育家。他1929年从德国学成回国,历经坎坷与艰辛,呕心沥血为我国生物学科研与教学事业作出了卓越的贡献。     

Mitochondrial Ca2+ transport and permeability transition pore opening and mitochondrial energetic status

The relationship between mitochondrial Ca2 transport and permeability transition pore (PTP) opening as well as the effects of mitochondrial energetic status on mitochondrial Ca2 transport and PTP opening were studied. The results showed that the calcium-induced calcium release from mitochondria (mClCR) induced PTP opening. Inhibitors for electron transport of respiratory chain inhibited mClCR and PTP opening. Partial recovery of electron transport in respiratory chain resulted in partial recovery of mClCR and PTP opening. mClCR and PTP opening were also inhibited by CCCP which eliminated transmembrane proton gradient. The results indicated that mitochondrial Ca2 transport and PTP opening are largely dependent on electron transport and energy coupling.     

Temperature-dependence and conformational basis of inositol 1,4,5-trisphosphate receptor regulated by Ca~(2 )

The inositol 1,4,5-trisphosphate (lnsP3) receptor was purified from bovine cerebellum and reconstituted in liposomes composed of phosphatidylcholine (PC) and phosphatidylethanola-mine (PE) (1:1) successfully. No effect of Ca2 concentration on [3H]-lnsP3 binding to unreconsti-tuted lnsP3 receptor could be observed either at 4℃ or at 25℃, whereas the effect of [Ca2 ] on reconstituted lnsP3 receptor depended on the temperature. The Ca2 concentration outside the proteolipsome ([Ca2 ]o) had no detectable effect on lnsP3 binding to lnsP3 receptor at 4℃. In contrast, with increase of [Ca2 ]o from 0 to 100 nmol/L at 25℃, the lnsP3 binding activity increased gradually. Then the lnsP3 binding activity was decreased drastically at higher [Ca2 ]0 and inhibited entirely at 50 nmol/L [Ca2 ]. Conformational studies on intrinsic fluorescence of the reconstituted lnsP3 receptor and its quenching by Kl and HB indicated that the global conformation of reconstituted lnsP3 receptor could not be affected by [Ca2 ]o at     

生物膜膜蛋白三维结构研究的现状与展望

1　生物膜膜蛋白三维结构研究的重要性与迫切性　　细胞是生命的基本结构与功能单位 .细胞的外周膜与细胞内的膜系统称为生物膜 .细胞的能量转换、信息识别与传递、物质运送和分配等基本生命现象都与生物膜密切相关 .生物膜是由蛋白质、脂类以及碳水化合物等组成的超分子体系 ,膜蛋白是膜功能的主要体现者 .生物膜膜蛋白可分为外周膜蛋白和内在膜蛋白 ,后者约占整个膜蛋白的 70 %～ 80 % ,它们部分或全部嵌入膜内 ,有的则是跨膜分布 ,如受体、离子通道、离子泵、膜孔、运载体(ｔｒａｎｓｐｏｒｔｅｒ)以及各种膜酶等等 .象水溶性蛋白质一样 …     

GM3对重建Gs与AC偶联功能的影响

将神经节苷脂ＧＭ３（Ｍｏｎｏｓｉａｌｏｇａｎｇｌｉｏｓｉｄｅ－ＧＭ３）通过保温法掺入到含激活型Ｇ蛋白（ＳｔｉｍｕｌａｔｏｒｙＧＴＰ－ｂｉｎｄｉｎｇｐｒｏｔｅｉｎ,Ｇｓ）与腺苷酸环化酶（ＡｄｅｎｙｌｙｌＣｙｃｌａｓｅ,ＡＣ）的脂酶体中,研究了ＧＭ３对Ｇｓ和ＡＣ偶联功能的影响。实验结果表明,在４－１０μｍｏｌ／Ｌ浓度范围的ＧＭ３增加ＡＣ的基础活力;在高于４μｍｏｌ／Ｌ时,ＧＭ３可显著抑制Ｇｓ激活ＡＣ的能力;而在ＧＭ３浓度高于１００μｍｏｌ／Ｌ的条件下,Ｇｓ结合ＧＴＰγＳ（Ｇｕａｎｏｓｉｎｅ５＇－Ｏ－（３－ｔｈｉｏｔｒｉｐｈｏｓｐｈａｔｅ））的活力受到明显抑制。随外源ＧＭ３浓度的增加,ＧＭ３对Ｇｓ激活ＡＣ的能力与对ＡＣ基础活力的影响似乎并不完全一致。这些结果提示,Ｇｓ与ＡＣ的解偶联对较低浓度的ＧＭ３的影响更加敏感。用荧光探剂ＭＣ５４０标记脂酶体,测量其荧光光谱的结果显示,随着ＧＭ３浓度增加,ＭＣ５４０的荧光强度增强,这说明外源性的ＧＭ３的掺入使膜脂质分子头部的堆积变得更加疏松。这可能提示,ＧＭ３介导的膜脂物理状态的变化是调节Ｇｓ与ＡＣ偶联功能的重要因素之一。     

脱血红素细胞色素C自发折叠的进一步验证

用胰蛋白酶水解结构聚丙烯酰胺凝胶电泳以及纳秒内源荧光衰减谱分析对鸡心脱血红素细胞色素Ｃ在透析复性过程的自发折叠现象作进一步确定，结果显示随着透析复性时间的增加，鸡心脱血红素细胞色素Ｃ对胰蛋白酶的水解敏感性逐渐下降，内源荧光寿命值增大，与此对应的马心脱血红素细胞色素Ｃ没有发生变化。