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1、天然无折叠蛋白质,Natively unfolded protein05生物技术 张蕾,纲要-Outlines,Brief retrospection Main CharactersNUP2P as an exampleNUPS function and advantagesRelevant research Concluding remarks,Begin now!,上世纪年代，提出了蛋白质变性理论在50 年代,丹麦蛋白质化学家林德斯屈莱姆-(Linderstro/m-Lang)提出了蛋白质的一级、二级和三级结构的结构层.,A brief history,上世纪90 年代初,开始发现几种蛋白
2、质,没有二级和三级结构,但依然具有蛋白质活性。天然无折叠的蛋白质(natively unfolded protein,NUP)也有称为固有无结构蛋白质(intrinsically unstructural protein,IUP)固有无序化蛋白质(intrinsically disordered protein)的。,PubMed Hits,1978 Some proteins do not fold because atypical aa composition:NMR:Highly charged functional tail of histone H5 is disordered199
3、4“Natively Denatured”term to describe behavior of tau protein a polypeptide contained in the amyloid plaques observed AD1996“Natively Unfolded”term introduced in conformational analysis of-synuclein,a protein implicated in AD Protein p21Wafi/Cipa/Sdi1 a functional component of cell cycle control mec
4、hanism have no discernable structure and is disordered from end to end1999“Intrinsically Unstructured Proteins”call for reassessment of the protein structure-function paradigm2002 Data suggest IUPs play key roles in cell-signalling,regulation and cancer 2003 IUPs assume no compact structural state i
5、n vivo,A brief history.,Main characters,Natively unfolded proteins lack ordered structure under conditions of neutral pH in vitro.Lack 3D stucture.It appears that natively unfolded proteins have low hydrophobicity and high net charge.,In vivo,they are likely to be stabilized by binding of specific t
6、argets,ligands(small molecules,substrates,cofactors,other proteins,nucleic acids,membranes,etc.).,它们的氨基酸组成上也有一定的特征,总体而言,此类蛋白质中的亲水氨基酸(例如,E、K、R、G、Q、S 和P)的含量升高,疏水氨基酸(例如I、L、V、W、F、Y、C 和N)的含量降低;就个别氨基酸而言,脯氨酸、赖氨酸和谷氨酸的含量显著升高,而芳香氨基酸的含量降低明显。如下几种氨基酸的比例与常见的球状蛋白质有很大的差别:,Asn Cys Glu Lys Phe Pro Trp Tyr通常的球蛋白 4.66
7、1.64 5.98 6.05 3.95 4.61 1.55 3.64NUP/NUD 2.06 0.61 14.26 10.43 1.66 12.07 0.32 1.42,NUP2P as an example,酵母的核孔复合物中的Nup2p 是一个NUP。其一些特性反映在图1 中.,NUP2P as an example,Nup2p 在氨基酸组成上,N、C、I、L、F、W、Y 和这些氨基酸比酵母蛋白质组中的平均水平低,而A、R、Q、E、G、K、P 和S 却比酵母蛋白质组中的平均水平高。Nup2p 的流体力学的性质也表现异常。,看这里！,另一个反映蛋白质紧密程度的参数是沉降系数S。一般是紧密程度
8、相似的蛋白质,分子质量大,则S 值大.然而,Nup2p 的S 值为2.9 小于分子质量比其小的清蛋白的4.7。Nup2p 的傅立叶转换红外光谱中,波数为1686、1671、1654、1637 和1625 cm-1 的峰,分别对应于转角、环形、无序环形、无序片层和片层的各种类型二级结构的特征吸收。由这些峰的强度可以推算出这些类型二级结构的含量:转角11.8%、环形22.2%、无序环形42.6%、无序片层16.2%和片层7.2%。,Nup2ps function,Nup2p NLS:nuclear localization signal Srp1p NPC:nuclear pore complex
9、,Key Words,Import of proteins containing a classical NLS into the nucleus is mediated by importinand importin.,Cells lacking NUP2 show a specific defect in both NLS import and Srp1p export,indicating that Nup2p is required for efficient bidirectional transport of Srp1p across the nuclear pore comple
10、x(NPC).,Nup2p is located at the nuclear side of the central gated channel of the NPC and provides a binding site for Srp1p via its amino-terminal domain.Nup2p effectively releases the NLS protein from importin-importin and and strongly binds to the importin heterodimer via Srp1p.,Functional classifi
11、cation of IUPs,Advantages,统计分析得到的另一个结论是,NUP 起作调节作用,因此,他们是“管家”的“助手”从生物学的角度看,NUP 似乎具有更多的优点:首先，不需要经过折叠就能行使作用其次，肽链不需折叠,因此,它们整条肽链中的更多位点可以与更多的分子结合,进而呈现多种功能第三，结构还可随外界的需求而改变,以一些分子作为模板进行折叠,Relevant Research,以31 种物种基因组研究的结果为基础,对基因组表达产物中天然无折叠的蛋白质和蛋白质中天然无折叠结构域(50 个氨基酸残基的片段)的比例进行分析,所得的数据表明,真核生物基因组表达产物中NUP 和蛋白质中天
12、然无折叠结构域(natively unfolded domain,NUD)的比例均比多数古细菌和真细菌高,这一统计结果,足以对蛋白质学科视为经典的蛋白质结构层次提出了挑战。,目前已经证实,这一类型的蛋白质可以定位于细胞的不同部位,多数NUP 存在于细胞核和细胞质中.与老年痴呆密切有关的Tau 蛋白与帕金森病有关的突触核蛋白,-2synuclein,Concluding remarks,The“unusual”unstructured and functional features of IUPs are being appreciated and its fully understanding is a new challenge in the post-genome era.,Concluding remarks,IUPs are a novel and unique protein category of the protein universe whose importance predicts a motivating biophysical endeavor for the coming years,All Is Well That Ends Well!,Thank You!,
