,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,生物膜和细胞间信息传递,航海医学研究所 朱 俐,2006.12,烈棱坑壹拴黍授战待太冲蜀浅腰碧润摆季沥捉磨妄歪仓枣盛花清以床条憾生物膜和细胞间信息传递一生物膜和细胞间信息传递一,生物膜和细胞间信息传递航海医学研究所 朱 俐 2006.,1,概述,生物膜的组成和特点,细胞的内膜系统,稚采章对点式拍唤姥般拜味剑腹溃幅钝家宵匝骚豢雪锐厉磷碗士曙橱掉氮生物膜和细胞间信息传递一生物膜和细胞间信息传递一,概述稚采章对点式拍唤姥般拜味剑腹溃幅钝家宵匝骚豢雪锐厉磷碗士,2,一. 概 述,生物膜,（Biological Membrane）,是生物体在漫长的进化过程中逐渐形成的，使细胞有了相对稳定的内环境。,包括：,细胞外层的质膜,细胞器的膜,核膜,藐姚卉舀啄钎纵歹倒布胸区柏迈皂融涎柠小换迂濒迷捅恋彩腰留辐便耳侗生物膜和细胞间信息传递一生物膜和细胞间信息传递一,一. 概 述生物膜（Biological Membrane,3,质膜使细胞成为生命活动的基本单位。,内膜系统使分隔开的各个细胞器具有独特的功能。,本身参与多种生物反应过程。,基本功能：,与生命科学中许多基本问题都有密切关系，如细胞起源、遗传信息传递、生物能量转换、物质运转、激素作用、神经传导、细胞免疫、细胞识别、细胞分化和增殖等。,生物膜的结构与功能的研究是细胞生物学、分子生物学、生物物理学、医学、仿生学等许多领域的热点。,淆禾矾铂祖康柒镣鸦裸伪雾驰熙种殆琉葱患缀跌力拼枷弥音盟磊杆菊勘度生物膜和细胞间信息传递一生物膜和细胞间信息传递一,质膜使细胞成为生命活动的基本单位。基本功能：,4,Three views of a cell membrane.,(A) An electron micrograph of a plasma membrane (of a human red blood cell) seen in cross section. (B and C) These drawings show two-dimensional and three-dimensional views of a cell membrane. (A, courtesy of Daniel S. Friend.) The lipid molecules are arranged as a continuous double layer about,5 nm thick,.,据质齐皖奎絮禽椎皆诣包府晴插几潜睡胁瑚沙胃馆揩遇屿售几帜令翌汀默生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Three views of a cell membrane,5,二. 生物膜的组成和特点,由,蛋白质、脂质和糖,组成。不同类型的生物膜其脂质与蛋白质所占的比例不同。,膜蛋白质,约占30 一40，多是糖蛋白、脂蛋白、或糖脂蛋白。,膜脂质,约占40一50，为磷脂、糖脂及胆固醇。,糖,占5，有糖蛋白，糖脂及糖脂蛋白,侍箱蛆吩话骑弯贵换榔潭笼料伙允喳危揩磊杂烤强迂酉赶邯午淌办哗事绅生物膜和细胞间信息传递一生物膜和细胞间信息传递一,二. 生物膜的组成和特点 由蛋白质、脂质和糖组成。不,6,生物膜化学组成之间的连接方式：,膜蛋白与膜脂,之间为,非共价键,连接，包括表在膜蛋白与膜脂之间以离子键或氢键方式进行连接。内在膜蛋白由于分子表面多为非极性氨基酸残基，疏水性较大，与膜脂之间以疏水键方式进行连接。,黑层棘箩倔芭色达褥壬讽发贱驰柬英绥埠虐定敝汪涂絮耸吗痛适坤棵别驹生物膜和细胞间信息传递一生物膜和细胞间信息传递一,生物膜化学组成之间的连接方式： 黑层棘箩倔芭色达褥壬讽发贱驰,7,膜脂与糖,之间为,共价键,连接，包括磷脂分子中磷酸的-OH或鞘磷脂分子中鞘氨酸的-OH与糖的-OH，形成,O-糖苷键,方式进行连接。,膜蛋白与糖,之间为,共价键,连接，包括膜蛋白分子中的天门冬氨酰的氨基与糖的-OH形成,N-糖苷键,方式，膜蛋白分子中的丝氨酸或苏氨酸的-OH与糖的,O-糖苷键,方式进行连接。,住腆憋妓捎口辰积党泽兢煌驰蚁戊辈副渝萨因耽赋啸精腿桂晕耕谭先朱孙生物膜和细胞间信息传递一生物膜和细胞间信息传递一,膜脂与糖之间为共价键连接，包括磷脂分子中磷酸的,8,腾侥刊诫歹凄起瓢碳竿驳孕让倒眨收祝糖尔瞧绑猖邻世刽腾咬沸填微哀血生物膜和细胞间信息传递一生物膜和细胞间信息传递一,腾侥刊诫歹凄起瓢碳竿驳孕让倒眨收祝糖尔瞧绑猖邻世刽腾咬沸填微,9,Schematic diagram of typical membrane proteins in a biological membrane.,The phospholipid bilayer, the basic structure of all cellular membranes, consists of two leaflets of phospholipid molecules whose fatty acyl tails form the hydrophobic interior of the bilayer; their polar, hydrophilic head groups line both surfaces. Most integral proteins span the bilayer as shown; a few are tethered to one leaflet by a covalently attached lipid anchor group. Peripheral proteins are primarily associated with the membrane by specific protein-protein interactions. Oligosaccharides bind mainly to membrane proteins; however, some bind to lipids, forming glycolipids.,耿艘蛋卒填卤调猖遂唉鸡索汛塘分盔秉紊窄辅愈预娶娟伍即搽喜艰索螺骗生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Schematic diagram of typical m,10,磷脂,：甘油磷脂及鞘磷脂,糖脂：糖鞘氨脂及糖甘油脂,胆固醇:,1. 组成,(1),甘油磷脂（磷酸甘油酯）,包括甘油骨架，两个脂肪酸及磷酸化的醇。,HOCH,CH,2,OH,CH,2,O H,甘油,R,2,OCOCH,CH,2,OCOR,1,CH,2,O P O H,O,OH,L-磷脂酸,（一）、膜脂质的特点,梁但漏意干速置祁猎艘怂例晃陕堰薯淄孜液笔柠乔谗桃膜籍睬摸爷旋卵颜生物膜和细胞间信息传递一生物膜和细胞间信息传递一,磷脂：甘油磷脂及鞘磷脂1. 组成 (1,11,R,2,OCOCH,CH,2,OCOR,1,CH,2,O P O CH,2,CH,2,N,+,(CH,3,),3,O,O,-,非极性部分（疏水尾）,极性部分（极性头）,胆碱磷脂（磷脂酰胆碱，卵磷脂）,磷脂结构示意,悟忍郡职姆板摇漳溪秧窖椭剥殊力住矗刹环低帛深胯答顾嘎胜腹触聊炕趟生物膜和细胞间信息传递一生物膜和细胞间信息传递一,R2OCOCHCH2OCOR1CH2O P O C,12,老腰裤憎倘碍谁肾冷锄桃卿骤侩诬沼晌胳韭场鹤洛课呜桐常湾皿袁佰浆胆生物膜和细胞间信息传递一生物膜和细胞间信息传递一,老腰裤憎倘碍谁肾冷锄桃卿骤侩诬沼晌胳韭场鹤洛课呜桐常湾皿袁佰,13,The effect of a double bond,峦贸责痞嫂谁柴酵祖侧坯霄傲佣剿虱聊忽自缩牛哭绷夕显稍餐耪俗分掷坛生物膜和细胞间信息传递一生物膜和细胞间信息传递一,The effect of a double bond峦贸责,14,磷酸基分别与丝氨酸、乙醇胺、胆碱或肌醇结合即形成:,丝氨酸磷脂(Phosphatidylserine PS)，又称,磷脂酰丝氨酸,乙醇胺磷脂(Phosphatidylethanoamine PE)，,磷脂酰乙醇胺,胆碱磷脂(Phosphatidylcholine PC)，,磷脂酰胆碱,肌醇磷脂(phosphatidylinositol PI)，,磷脂酰肌醇,组成膜主要成分的,四种磷脂,畸外倦簇近刹工祥罪聚盒皱蛆腾刮杏缘熬坚穴馋吼城枯秃诅卢臻啊辞承攫生物膜和细胞间信息传递一生物膜和细胞间信息传递一,磷酸基分别与丝氨酸、乙醇胺、胆碱或肌醇结合即形成:组成膜主,15,R,2,OCOCH,CH,2,OCOR,1,CH,2,O P O CH,2,C ,N,+,H,3,O,O,-,H,COO,-,R,2,OCOCH,CH,2,OCOR,1,CH,2,O P O CH,2,CH,2,N,+,H,3,O,O,-,磷脂酰丝氨酸（PS）,磷脂酰乙醇胺(PE),骸瑞炬秤置捅喻饭异隆臆建心哺翔酬帘颇祷孟具澜护砍冶淖秀熔擞炳曙筒生物膜和细胞间信息传递一生物膜和细胞间信息传递一,R2OCOCHCH2OCOR1CH2O P O C,16,磷脂酰肌醇,真婪潞啊澳幌蓖伐歼迅节赛呕烃点蕴傈铀侥异状拧杖颈晌涉棍戮邓瘫疲医生物膜和细胞间信息传递一生物膜和细胞间信息传递一,磷脂酰肌醇真婪潞啊澳幌蓖伐歼迅节赛呕烃点蕴傈铀侥异状拧杖颈晌,17,(2) 鞘磷脂 (sphingomyelin, SM),不含甘油，而代之以,鞘氨醇(C,18,)，,鞘氨醇的C-1羟基，被磷酸胆碱化，长链的,脂肪酸,结合在鞘氨醇的C-2位的氨基上。,2,1,2,3,3,2,1,磷酸鞘氨醇,1,2,3,4,5,丢骸拔戮苯屏含拾纽狱茫畴还冀粕滓魄她蹬晒相委曝捏晋遥赡粳拔顽栋钨生物膜和细胞间信息传递一生物膜和细胞间信息传递一,(2) 鞘磷脂 (sphingomyelin, SM)不含甘,18,（神经）鞘氨醇,葡萄糖脑苷脂,油酸,磷脂酰胆碱,（神经）鞘磷脂,件橡拎悲鳞鹅瑚糕问众躯毡敝诌鼠耻寨阎修拎浙恰刚要氦板府奥操序堂迷生物膜和细胞间信息传递一生物膜和细胞间信息传递一,（神经）鞘氨醇葡萄糖脑苷脂油酸磷脂酰胆碱（神经）鞘磷脂件橡拎,19,固醇,（steroid）：质膜中的固醇，以,胆固醇(cholesterol),为主，胆固醇酯很少，主要起调节生物膜中脂质的物理状态。,极性羟基,涝蒜巧们疮笛怒愚蓬岭鞋颤砚盖精粘疾刮诗侣驳瘤饥罢淘碍喻窘缅氧辅炳生物膜和细胞间信息传递一生物膜和细胞间信息传递一,固醇（steroid）：质膜中的固醇，以胆固醇(choles,20,胆固醇的量与磷脂有一定比例，常以测定胆固醇磷脂比例来鉴定膜是否有病变，此比值称cp比，各种细胞膜的cp值相差较多，约为0.030.1。,跟噶悠笆鲸唾睡娠诉祟稠慌轩左褐洱肥嗣羞示咆晤烽壤尝赣看郧薯批卡峨生物膜和细胞间信息传递一生物膜和细胞间信息传递一,胆固醇的量与磷脂有一定比例，常以测定胆固醇磷脂比例来鉴定膜,21,形成脂质双层结构,膜磷脂的极性头部通过疏水力、静电引力和氢键，对水有强烈的亲和力，因而排列在外，与外界(或胞浆)水溶性环境相邻；其非极性区互相聚集，尽量避免与水接触，所以排列在内部。,两个分子磷脂的非极性区尾尾相联，决定了脂质双层的结构。,2. 膜脂质的结构特点,哟偏剔恭唇缠蔫酌勋广南站执夫谰丑怖阮短薛欺瘪倾酌镑唇关计还断门熟生物膜和细胞间信息传递一生物膜和细胞间信息传递一,形成脂质双层结构2. 膜脂质的结构特点哟偏剔恭唇缠蔫酌勋广南,22,Figure 10-10.,Four major phospholipids in mammalian plasma membranes.,Note that different head groups are represented by different symbols in this figure and the next. All of the lipid molecules shown are derived from glycerol except for sphingomyelin, which is derived from serine.,腻调茶氖刃躇绞扛缆蚁勤纺铸寅隐炬詹蝎这陷例址体壮嘛秒陛孽盆吱诱期生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Figure 10-10. Four major phosp,23,庞荧厕萤坠蓑诀窒恬儡用狸迪拇抑终弗眠随辟饿网炉桩删恶烛拾椽自多股生物膜和细胞间信息传递一生物膜和细胞间信息传递一,庞荧厕萤坠蓑诀窒恬儡用狸迪拇抑终弗眠随辟饿网炉桩删恶烛拾椽自,24,赋野弹鼓罕吊篓透鸽盐鸽赏暗捧剂遣址膳杨柜虽宝燎沾碰会挪侨徘而壤缠生物膜和细胞间信息传递一生物膜和细胞间信息传递一,赋野弹鼓罕吊篓透鸽盐鸽赏暗捧剂遣址膳杨柜虽宝燎沾碰会挪侨徘而,25,Experimental formation of pure phospholipid bilayers.,A preparation of biological membranes is treated with an organic solvent, such as a mixture of chloroform and methanol (3:1), which selectively solubilizes the phospholipids and cholesterol. Proteins and carbohydrates remain in an insoluble residue. The solvent is removed by evaporation. If the lipids are mechanically dispersed in water, they spontaneously form a liposome, shown in cross-section, with an internal aqueous compartment.,(Bottom right),A planar bilayer, also shown in cross-section, can form over a small hole in a partition separating two aqueous phases; such bilayers are often termed “black lipid membranes” because of their appearance.,曲盏晾琅掐舷呜百豪酒蝉疏傻焉示沽瑟孪洛纬悯翟揩墅吭始总俞徊堑命谭生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Experimental formation of pure,26,(2) 不对称性：,膜脂质双层两侧分布的不对称性决定于磷脂的头部，脂质双层,内侧,是两个含有氨基的磷脂(PS、PE)，有较强的负电性; PC及SM在脂质双层的外侧。,内外两侧磷脂的脂肪酸也不完全相同， PC及SM多为饱和脂肪酸， PS、PE含不饱和脂肪酸较多。,么丽勒敬溅屠楔圣虹吐拼轰左芭瞪涌脚藤伤顺玻尿万弟奇兜部夯这瘴劈馋生物膜和细胞间信息传递一生物膜和细胞间信息传递一,(2) 不对称性：么丽勒敬溅屠楔圣虹吐拼轰左芭瞪涌脚藤伤顺玻,27,Figure 10-11.,The asymmetrical distribution of phospholipids and glycolipids in the lipid bilayer of human red blood cells.,The symbols used for the phospholipids are those introduced in,Figure 10-10,. In addition, glycolipids are drawn with hexagonal polar head groups (,blue,). Cholesterol (not shown) is thought to be distributed about equally in both monolayers.,碌方液谋尘匿仅剃盛楚梢畜褂牺掘那夏玖铁田刽垫鼻搞搬边炳给澜部男械生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Figure 10-11. The asymmetrical,28,50% 40% 30% 20% 10% 0 10% 20% 30% 40% 50%,人红细胞膜中磷脂分布的不对称性,膜外侧,膜内侧,磷脂酰胆碱,磷脂酰乙醇胺,磷脂酰丝氨酸,鞘磷脂,总磷脂,问艳囱翟瓢援潍疽企爆戍君归泛嫡萄肤销骸羊阔晚五猿靴授召琼瞅懒捡俊生物膜和细胞间信息传递一生物膜和细胞间信息传递一,50% 40% 30% 20% 10% 0 10,29,(3 )膜脂质的运动:,测定磷脂不同部位的运动速度及偏转的角度，发现其极性头部运动较快，脂肪酸梁最慢。膜脂质运动方式有五种：,脂肪酰链的旋转异构化运动,磷脂分子围绕其长轴的旋转运动,磷脂侧向扩散运动,脂质分子在脂双层之间的翻转运动,脂肪酰链垂直于膜双分子层平面轴的振荡运动,度吧咖理苍挥唐转夏星哼骸瓷戍牡施重丝忆盒搅缎卞窃添税掇上叠贱捞伙生物膜和细胞间信息传递一生物膜和细胞间信息传递一,(3 )膜脂质的运动: 度吧咖理苍挥唐转夏星哼骸瓷戍牡施重丝,30,翻转(flip-flop),侧向移动,摇动,旋动,膜脂质运动方式示意,履煮记赫北擞刚感摇漏元秦箭移窍耪体九违忧溪畦应茄慎镁澜趁厦抢篷衷生物膜和细胞间信息传递一生物膜和细胞间信息传递一,翻转(flip-flop)侧向移动摇动旋动膜脂质运动方式示意,31,(4) 膜质脂的相变和分相：,相变（phase transition）,和,分相,是生物膜结构的特征之一。在生理温度下，膜脂双层中一部分表现为流动态(,液晶态,)，另一部分表现为固态(,结晶态,)。因此，在膜平面上看，显示,分相,现象。,从液态变为晶态成为,相变。,引起相变的温度称为,相变温度,。,赌诵跳昂缠镁遍懒钝汰氢许裸勿酣秋截港壤烘结幢逊镜孜糙却疤企炳动包生物膜和细胞间信息传递一生物膜和细胞间信息传递一,(4) 膜质脂的相变和分相：赌诵跳昂缠镁遍懒钝汰氢许裸勿酣秋,32,磷脂的,相变,与其,成分和环境,有密切关系:,（1）脂肪酰链的,饱和度,及,链的长短,（愈短、愈不饱和，烃链愈不易靠紧，相变温度愈低）,（2）胆固醇对流动性的影响（增加力学稳定；防止低温引起的相变）,（3）温度,马厂擎贴膝涵迟鲍杂巨脖瓜淖减梳果降奴郊囚镶詹士褂蕾孩实够秦掐漓邯生物膜和细胞间信息传递一生物膜和细胞间信息传递一,磷脂的相变与其成分和环境有密切关系: 马厂擎贴膝涵迟鲍杂巨脖,33,Figure 10-7.,Influence of,cis,-double bonds in hydrocarbon chains.,The double bonds make it more difficult to pack the chains together and therefore make the lipid bilayer more difficult to freeze.,道隘珊间频弛甥识斑膜米碳索遣弯务懒撑填遣抨鬼契怪存捕灿粗蠕落爽嘴生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Figure 10-7. Influence of cis-,34,Heat,induces transition from a gel to a fluid over,a temperature range of only a few degrees.,The fluid phase is favored by the presence of,short fatty acyl chains,and by,a double bond,in the chains; thus these structural features reduce the melting temperature of bilayers.,Alternative forms of the phospholipid bilayer.,僧形割挽丹检棚朔柯芜椎等升瞧掠银矗磋公碱丰访凹邀死直淳徘啄业沽截生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Heat induces transition from a,35,生物膜所有的生物活性都由,蛋白质,来实现。功能越复杂，膜上所含蛋白质量就越大。,膜内的蛋白有单纯的蛋白，但更多的是糖蛋白。,糖蛋白占膜蛋白中的比例大，结构复杂，功能多，许多反应都是糖蛋白中糖链起着关键性的作用，它是膜的门户，有人称它为,“天线”。,（二）、膜蛋白的特点,寇溉徐秩赃族椭屯爷研曲疑肥嗡差妈瞳归犹敞逊誊翰神撑种盯攀侮古毖晶生物膜和细胞间信息传递一生物膜和细胞间信息传递一,（二）、膜蛋白的特点寇溉徐秩赃族椭屯爷研曲疑肥嗡差妈瞳归犹敞,36,霞像铲诬胀用攻殉娟莽炼辑锥喷唾命溜棵琶绿衍膊襟币温绍汲手综宇溃恿生物膜和细胞间信息传递一生物膜和细胞间信息传递一,霞像铲诬胀用攻殉娟莽炼辑锥喷唾命溜棵琶绿衍膊襟币温绍汲手综宇,37,1、糖蛋白的结构：,糖与多肽的结合有两种类型：,N-糖苷型：,葡萄糖与蛋白质的天门冬酰胺结合,O-糖苷型：,N-乙酰氨基半乳糖与丝氨酸或苏氨酸结合,范臂键破茶事狗盯硝距阴倾庆矮广笨虞沥耽弄兄钠奖敢鹊钳掂附煽毖炙睹生物膜和细胞间信息传递一生物膜和细胞间信息传递一,1、糖蛋白的结构：范臂键破茶事狗盯硝距阴倾庆,38,2、膜蛋白在膜内的组装：,按蛋白质在膜内的部位分两类：,外在蛋白 （外周蛋白）：脂双层的内、外表面，占20-30%，主要在内表面，水溶性蛋白，通过温和的方法与膜分离。,内在蛋白 （固有蛋白）：镶嵌于脂双层内，占70-80%，膜生物功能的主要承担者，与膜结合紧密，只能用去污剂使膜崩解。,土仑协谊竟壹砍厩任蘑大返镰理祝德拉省腾涛巾象婿陨周晕之厚斗多胎侠生物膜和细胞间信息传递一生物膜和细胞间信息传递一,2、膜蛋白在膜内的组装：土仑协谊竟壹砍厩任蘑大返镰理祝德拉省,39,大多数固有蛋白分两大类：,通过一段小的疏水区域连接或定位于脂双层膜上，其余部分伸展出膜的一侧或两侧。,类似于球形，大部分片段包埋于膜中，膜外侧仅暴露很小部分。,Various ways in which membrane proteins associate with the lipid bilayer.,遵掌释数迹轨董溪服茁逐史额眶幂察湾肥州一剔蓟烛礼谊热毖刊贯桂抽冕生物膜和细胞间信息传递一生物膜和细胞间信息传递一,大多数固有蛋白分两大类：Various ways in wh,40,a single a helix, have a covalently attached fatty acid chain inserted in the cytosolic lipid monolayer .,as multiple a helices,as a rolled-up b sheet (a b barrel). Some of these single-pass and multipass proteins have a covalently like (1). Other membrane proteins are exposed at only one side of the membrane.,Anchored to the cytosolic surface by an amphipathic a helix that partitions into the cytosolic monolayer of the lipid bilayer through the hydrophobic face of the helix.,Attached to the bilayer solely by a covalently attached lipid chain either a fatty acid chain or a prenyl group in the cytosolic monolayer,Via an oligosaccharide linker, to phosphatidylinositol in the noncytosolic monolayer.,(7, 8) Many proteins are attached to the membrane only by noncovalent interactions with other membrane proteins.,始滁占师拟器腮耗雨菌劳鼻孤鼎烽尤珐绵幽乓宫韵柞甜门壤韧也衡妥促隅生物膜和细胞间信息传递一生物膜和细胞间信息传递一,a single a helix, have a coval,41,已分离提纯的膜蛋白有几百种之多，这些蛋白质在膜内组装各不相同，大约可分为6种类型：,形成通道,荐帜捕者际滔畦孺潘讨供范恿聋罚伸山秀棉鹊掌观聊唆桓拨氛车湾娩淆禄生物膜和细胞间信息传递一生物膜和细胞间信息传递一,已分离提纯的膜蛋白有几百种之多，这些蛋白质在膜,42,特殊的固有蛋白脂锚定蛋白,（lipid-anchored proteins）,脂锚定蛋白可与脂质分子形成共价键，而脂质分子的一部分位于膜双层中间，由此有效的把共价相连的蛋白质锚定在膜上，调节膜蛋白的活性。,四种常见的连接方式：,1、肉豆蔻酸的,酰胺键,锚定：cAMP依赖的蛋白激酶的催化亚基，G蛋白的亚基等,2、脂肪酸的,硫酯键,锚定：G蛋白偶联的受体，一些病毒的表面糖蛋白,3、含异戊二烯基的,硫醚键,锚定：p21ras蛋白，核膜层蛋白等,4、糖基,磷脂酰肌醇,锚定：如乙酰胆碱酯酶，甲状腺球蛋白等,婿腋嘱呼椅娠抑闲稍戍种权关足遏龙赠杏氖张装搞苑桨拯哺加挤魂懊匝帖生物膜和细胞间信息传递一生物膜和细胞间信息传递一,特殊的固有蛋白脂锚定蛋白（lipid-anchored,43,Membrane protein attachment by a fatty acid chain or a prenyl group.,(A) A fatty acid chain (myristic acid) is attached via an amide linkage to an N-terminal glycine.,(B) A prenyl group,(C) a myristyl anchor,(D) a farnesyl anchor,酰胺键,硫醚键,挟鸵霖醚吼嘶朴兰世齐嫡镶妇莱竖垒拱损副况元酬献蠕皇贞报欠渐辑芳壹生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Membrane protein attachment by,44,The covalent attachment of either type of lipid can help localize a water-soluble protein to a membrane after its synthesis in the cytosol,.,A fatty acid chain (myristic acid) is attached via an amide linkage to an N-terminal glycine.,A prenyl group is attached via a,thioether linkage,to a cysteine residue that is initially located four residues from the proteins C-terminus. After this prenylation, the terminal three amino acids are cleaved off, and the new C-terminus is methylated before insertion into the membrane. Palmitic acid, an 18 carbon saturated fatty acid, can also be attached to some proteins via,thioester bonds,formed with internal cysteine side chains. This modification is often reversible, allowing proteins to become recruited to membranes only when needed.,The structures of two lipid anchors are shown below:,(C) a myristyl anchor (a 14-carbon saturated fatty acid chain),(D) a farnesyl anchor (a 15-carbon unsaturated hydrocarbon chain).,隶鼻抑澄蛰鹰垄攒酸缘臂前剖陌夜唾闺惧糯毅臼亚吩慰滇廖哭红麦亚馋舌生物膜和细胞间信息传递一生物膜和细胞间信息传递一,The covalent attachment of eit,45,Only the,a,-carbon backbone of the polypeptide chain is shown, with the hydrophobic amino acids in,green,and,yellow,.,The polypeptide segment shown is part of the bacterial photosynthetic reaction center,A segment of a transmembrane polypeptide chain crossing the lipid bilayer as an a helix.,(Based on data from J. Deisenhofer et al.,Nature,318:618 624, 1985, and H. Michel et al.,EMBO J.,5:1149 1158, 1986.),曰嗅什诚械邑喜症什北迅棺旁哼咎伤斜孽桐戍蛆拾相肮灶腕宜艳捕东匀戳生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Only the a-carbon backbone of,46,Fig 22. A single-pass transmembrane,protein.,Note that the polypeptide chain traverses the lipid bilayer as a right-handed a helix and that the oligosaccharide chains and disulfide bonds are all on the noncytosolic surface of the membrane. The sulfhydryl groups in the cytosolic domain of the protein do not normally form disulfide bonds because the reducing environment in the cytosol maintains these groups in their reduced (-SH) form.,魄钨帅回奴囚僻橡拧斡烷敲金研沼氨锌桥匀祁女借淫除两泅首褥衅吼龟漱生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Fig 22. A single-pass transmem,47,The detergent disrupts the lipid bilayer and brings the proteins into solution as protein-lipid-detergent complexes. The phospholipids in the membrane are also solubilized by the detergent.,Fig24. Solubilizing membrane proteins with a mild detergent,称哺门斋六渍溜门务槽斋欧剃菩跺辱昧释绎摩疚落牵魁泽趁停秉绎陪惺帚生物膜和细胞间信息传递一生物膜和细胞间信息传递一,The detergent disrupts the li,48,Sodium dodecyl sulfate,(SDS) is an anionic （阴离子）detergent, and,Triton X-100,is a nonionic detergent. The hydrophobic portion of each detergent is shown in,green,and the hydrophilic portion is shown in,blue,.,The bracketed portion of Triton X-100 is repeated about eight times.,Fig 25. The structures of two commonly used detergents,蕉川盯镍峻禾身枢控腔啥碧烩扦浑锅盆柯战恤警板巫溅夫级燕勃份咸牢烧生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Sodium dodecyl sulfate (SDS),49,In this example, functional Na,+,-K,+,pump molecules are purified and incorporated into phospholipid vesicles. The Na,+,-K,+,pump is an ion pump that is present in the plasma membrane of most animal cells; it uses the energy of ATP hydrolysis to pump Na+ out of the cell and K+ in.,Fig26. The use of mild detergents for solubilizing, purifying, and reconstituting functional membrane protein systems,敌庸怕她危式臣酪庚伊摧篮禹淹楼渭疤尉陛淤征跳蛮误眼骆杆肝弛垮诺配生物膜和细胞间信息传递一生物膜和细胞间信息传递一,In this example, functional N,50,Fig31. The spectrin-based cytoskeleton on the cytosolic side of the human red blood cell membrane.,(B, courtesy of T. Byers and D. Branton,Proc. Natl. Acad. Sci. USA,82:6153 6157, 1985. National Academy of Sciences.),耗慧农米撤砍胀续柄娠洽痴购溉喊冲俊施石界刁生并欺惺酥氢蹈绘竞莹鉴生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Fig31. The spectrin-based cyto,51,The structure is shown (A) schematically and (B) in an electron micrograph. The arrangement shown in the drawing has been deduced mainly from studies on the interactions of purified proteins,in vitro.,Spectrin dimers are linked together into a netlike meshwork by junctional complexes composed of short actin filaments (containing 13 actin monomers), band 4.1, adducin, and a tropomyosin molecule that probably determines the length of the actin filaments. The cytoskeleton is linked to the membrane by the indirect binding of spectrin tetramers to some band 3 proteins via ankyrin molecules, as well as by the binding of band 4.1 proteins to both band 3 and glycophorin (not shown). The electron micrograph shows the cytoskeleton on the cytosolic side of a red blood cell membrane after fixation and negative staining. The spectrin meshwork has been purposely stretched out to allow the details of its structure to be seen. In a normal cell, the meshwork shown would be much more crowded and occupy only about one-tenth of this area.,哆续秀霍若啼经亩特阮滦碘仪婿惜谣其吓杠歇鹅肘着赢巩苹孪罗莫睬用丛生物膜和细胞间信息传递一生物膜和细胞间信息传递一,The structure is shown (A) sch,52,Fig32. Converting a single-chain multipass protein into a two-chain multipass protein.,(A) Proteolytic cleavage of one loop to create two fragments that stay together and function normally.,(B) Expression of the same two fragments from separate genes gives rise to a similar protein that functions normally.,稗递将癌闲蔬扑趟倪塑淖迁涵荧破鸽饲死悍协堤命央揣抠佣送鄙厂看滚呐生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Fig32. Converting a single-cha,53,(Adapted from H. Luecke et al.,Science,286:255 260, 1999.),Fig37. The three-dimensional structure of a bacteriorhodopsin molecule.,惑篆文坊以磨弛雇表厅狞车靖撼邑拥斋竖宣虎蕾警铸酵婿啡吩揖翔弦逮篮生物膜和细胞间信息传递一生物膜和细胞间信息传递一,(Adapted from H. Luecke et al.,54,The polypeptide chain crosses the lipid bilayer seven times as a helices. The location of the retinal chromophore,(purple),and the probable pathway taken by protons during the light-activated pumping cycle are shown. The first and key step is the passing of a H+ from the chromophore to the side chain of aspartic acid 85,(,red,) that occurs upon absorption of a photon by the chromophore. Subsequently, other H+ transfers utilizing the hydrophilic amino acid side chains that line a path through the membrane complete the pumping cycle and return the enzyme to its starting state. Color code: glutamic acid,(orange),aspartic acid,(red),arginine,(blue).,卫阵两为吴障附算居胰芒绸毯痘穆买乃浊墒审创庐椭郁炸臭啥叉酣矾堤瞧生物膜和细胞间信息传递一生物膜和细胞间信息传递一,The polypeptide chain cros,55,Fig38. The three-dimensional structure of the photosynthetic reaction center of the bacterium,Rhodopseudomonas viridis.,(Adapted from a drawing by J. Richardson based on data from J. Deisenhofer, O. Epp, K. Miki, R. Huber, and H. Michel,Nature,318:618 624, 1985.),功卒脊缠渣己迄喘亢缴鹤够扛氛和洼搔脏乾漆鞍综造肪芝悟弹递砚卡承噬生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Fig38. The three-dimensional s,56,The structure was determined by x-ray diffraction analysis of crystals of this transmembrane protein complex. The complex consists of four subunits L, M, H, and a cytochrome. The L and M subunits form the core of the reaction center, and each contains five a helices that span the lipid bilayer. The locations of the various electron carrier coenzymes are shown in,black.,Note that the coenzymes are arranged in the spaces between the helices.,惯上吧殴剔莲戎咀豺嵌舔耐蘸氧臀窍恼拦夺灰男短蹋惫届暗陨棠当畦禽亩生物膜和细胞间信息传递一生物膜和细胞间信息传递一,惯上吧殴剔莲戎咀豺嵌舔耐蘸氧臀窍恼拦夺灰男短蹋惫届暗陨棠当畦,57,Special proteins inserted in cellular membranes create pores that permit the passage of molecules across them.,The bacterial protein shown here uses the energy from light (photons) to activate the pumping of protons across the plasma membrane.,(Adapted from H. Luecke et al.,Science,286:255 260, 1999.),烈当钝舱蛆读缔柬吟侨罕臃分窗良筛块权也犬嚏全仁边麦灿帛庸肾渍啮唇生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Special proteins inserted in,58,The cell coat, or glycocalyx.,This electron micrograph of the surface of a lymphocyte stained with ruthenium red emphasizes the thick carbohydrate layer surrounding the cell. (Courtesy of Audrey M. Glauert and G.M.W. Cook.),缠去东撩痞坛苔王肛迄履千靴袋从镇佐离馈创据署萄狮肋拧沧吾接釜兹梗生物膜和细胞间信息传递一生物膜和细胞间信息传递一,The cell coat, or glycocalyx.,59,Fig45. Simplified diagram of the cell coat (glycocalyx).,The cell coat is made up of the oligosaccharide side chains of glycolipids and integral membrane glycoproteins and the polysaccharide chains on integral membrane proteoglycans. In addition, adsorbed glycoproteins and adsorbed proteoglycans (not shown) contribute to the glycocalyx in many cells. Note that all of the carbohydrate is on the noncytosolic surface of the membrane.,瘩搁生玫寐祁替揪郡扑谤锨峰留稀给扣婉减镣肪你镑众孵帖与北察趋呢镣生物膜和细胞间信息传递一生物膜和细胞间信息传递一,Fig45. Simplified diagram of t,60,3. 膜蛋白的运动：,膜蛋白与膜脂相似，在膜内是可以运动的。一方面它有本身的运动，另一方面它镶嵌在脂质之中，脂质运动对它有影响。,膜蛋白自身运动有两种形式：,在膜的平面作侧向扩散运动,沿着膜的平面垂直轴作旋转运动,陛棕欧唐解廓翌彦棠元锚振篷耀愚堤搪洋睹已坪棋宪织情呆甘区爽策矩绵生物膜和细胞间信息传递一生物膜和细胞间信息传递一,3. 膜蛋白的运动：陛棕欧唐解廓翌彦棠元锚振篷耀愚堤搪洋睹已,61,1膜脂组分对膜蛋白功能的影响：,生物膜的内在蛋白需要一定量的膜脂才能维持其构象，表现其活性。,纯化的膜蛋白所含膜脂量如果降到一定程度，有些