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Crystal structure of the ribonucleoprotein core of the signal recognition particle

SCIENCE 2000年第5456期287卷 1232-+页

作者： Batey, RT Rambo, RP Lucast, L Rha, B Doudna, JA Yale Univ Howard Hughes Med Inst New Haven CT 06511 USA Yale Univ Dept Mol Biophys & Biochem New Haven CT 06511 USA

The signal recognition particle (SRP), a protein-RNA complex conserved in all three kingdoms of Life, recognizes and transports specific proteins to cellular membranes for insertion or secretion. We describe here the 1.8 angstrom crystal structure of the universal core of the SRP, revealing protein recognition of a distorted RNA minor groove. Nucleotide analog interference mapping demonstrates the biological importance of observed interactions, and genetic results show that this core is functional in vivo. The structure explains why the conserved residues in the protein and RNA are required for SRP assembly and defines a signal sequence recognition surface composed of both protein and RNA.

关键词：氨基酸序列细菌蛋白质类/化学细菌蛋白质类/代谢碱基配对结合部位细胞膜/代谢结晶学 X线大肠杆菌/化学大肠杆菌/遗传学大肠杆菌/代谢大肠杆菌蛋白质类鸟苷三磷酸/代谢氢键合镁/代谢模型分子分子序列数据核酸构象钾/代谢蛋白质结合蛋白质构象蛋白质结构二级蛋白质结构三级 RNA 细菌/化学 RNA 细菌/遗传学 RNA 细菌/代谢信号识别颗粒/化学信号识别颗粒/代谢转化细菌水/代谢

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Association of Escherichia coli ribosomes with the inner membrane requires the signal recognition particle receptor but is independent of the signal recognition particle

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2000年第9期97卷 4621-4626页

作者： Herskovits, AA Bibi, E Weizmann Inst Sci Dept Biol Chem IL-76100 Rehovot Israel

In mammalian cells, as well as Escherichia coli, ribosomes translating membrane proteins interact cotranslationally with translocons in the membrane, and this interaction is essential for proper insertion of nascent polypeptides into the membrane. Both the signal recognition particle (SRP) and its receptor (SR) are required for functional association of ribosomes translating integral membrane proteins with the translocon. Herein, we confirm that membrane targeting of E. coli ribosomes requires the prokaryotic SR alpha homolog FtsY in vivo. Surprisingly, however, depletion of the E. coli SRP54 homolog (Ffh) has no significant effect on binding of ribosomes to the membrane, although Ffh depletion is detrimental to growth. These and other observations suggest that, in E. coli. SRP may operate downstream of SR-mediated targeting of ribosomes to the plasma membrane.

关键词：阿拉伯糖/代谢细菌蛋白质类/代谢细胞膜/代谢大肠杆菌/遗传学大肠杆菌/生长和发育大肠杆菌/代谢动力学膜蛋白质类/遗传学蛋白质生物合成受体胞质和核/代谢受体肽/代谢核糖体/代谢信号识别颗粒/代谢

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A novel precursor recognition element facilitates posttranslational binding to the signal recognition particle in chloroplasts

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2000年第4期97卷 1926-1931页

作者： DeLille, J Peterson, EC Johnson, T Moore, M Kight, A Henry, R Univ Arkansas Dept Biol Sci Fayetteville AR 72701 USA

Signal recognition particles (SRPs) in the cytosols of prokaryotes and eukaryotes are used to target proteins to cytoplasmic membranes and the endoplasmic reticulum, respectively. The mechanism of targeting relies on cotranslational SRP binding to hydrophobic signal sequences. An organellar SRP identified in chloroplasts (cpSRP) is unusual in that it functions posttranslationally to localize a subset of nuclear-encoded thylakoid proteins. In assays that reconstitute thylakoid integration of the light harvesting chlorophyll-binding protein (LHCP), stromal cpSRP binds LHCP posttranslationally to form a cpSRP/LHCP transit complex, which is believed to represent the LHCP form targeted to thylakoids. In this investigation, we have identified an 18-aa sequence motif in LHCP (L18) that, along with a hydrophobic domain, is required for transit complex formation. Fusion of L18 to the amino terminus of an endoplasmic reticulum-targeted protein, preprolactin, led to transit complex formation whereas wild-type preprolactin exhibited no ability to form a transit complex. In addition, a synthetic L18 peptide, which competed with LHCP for transit complex formation, caused a parallel inhibition of LHCP integration. Translocation of proteins by the thylakoid Sec and Delta pH transport systems was unaffected by the highest concentration of L18 peptide examined. Our data indicate that a motif contained in L18 functions in precursor recruitment to the posttranslational SRP pathway, one of at least four different thylakoid sorting pathways used by chloroplasts.

关键词：氨基酸序列结合竞争性生物转运叶绿体/代谢内质网/代谢光获取蛋白复合物分子序列数据肽碎片/药理学光合作用中心复合蛋白质类/遗传学光合作用中心复合蛋白质类/代谢催乳素/代谢蛋白质结合蛋白质前体/代谢蛋白质加工转译后蛋白分选信号/代谢重组蛋白质类酿酒酵母蛋白质类信号识别颗粒/代谢类囊体/代谢

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Role of 4.5S RNA in assembly of the bacterial signal recognition particle with its receptor

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SCIENCE 2000年第5471期288卷 1640-1643页

作者： Peluso, P Herschlag, D Nock, S Freymann, DM Johnson, AE Walter, P Univ Calif San Francisco Howard Hughes Med Inst San Francisco CA 94143 USA Univ Calif San Francisco Dept Biochem & Biophys San Francisco CA 94143 USA Stanford Univ Dept Biochem Stanford CA 94305 USA Texas A&M Univ Syst Hlth Sci Ctr College Stn TX 77843 USA

The mechanism by which a signal recognition particle (SRP) and its receptor mediate protein targeting to the endoplasmic reticulum or to the bacterial plasma membrane is evolutionarily conserved. in Escherichia coli, this reaction is mediated by the Ffh/4.5S RNA ribonucleoprotein complex (Ffh/4.5S RNP;the SRP) and the FtsY protein (the SRP receptor). We have quantified the effects of 4.5S RNA on Ffh-FtsY complex formation by monitoring changes in tryptophan fluorescence. Surprisingly, 4.5S RNA facilitates both assembly and disassembly of the Ffh-FtsY complex to a similar extent. These results provide an example of an RNA molecule facilitating protein-protein interactions in a catalytic fashion.

关键词：细菌蛋白质类/化学细菌蛋白质类/代谢催化作用大肠杆菌/代谢大肠杆菌蛋白质类鸟苷二磷酸/代谢鸟苷三磷酸/代谢鸟苷酰亚胺二磷酸/代谢动力学模型化学核酸构象蛋白质结合蛋白质构象蛋白质结构三级 RNA 细菌/化学 RNA 细菌/代谢受体胞质和核/化学受体胞质和核/代谢核糖核蛋白类/化学核糖核蛋白类/代谢信号识别颗粒/化学信号识别颗粒/代谢光谱法荧光热力学色氨酸

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The α and β subunit of the nascent polypeptide-associated complex have distinct functions

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JOURNAL OF BIOLOGICAL CHEMISTRY 2000年第48期275卷 37838-37845页

作者： Beatrix, B Sakai, H Wiedmann, M Mem Sloan Kettering Canc Ctr Cellular Biochem & Biophys Program New York NY 10021 USA Nagasaki Univ Sch Dent Dept Pharmacol Nagasaki 852 Japan

Nascent polypeptide-associated complex (NAC) is probably the first cytosolic protein to contact nascent polypeptide chains emerging from ribosomes. In this way NAC prevents inappropriate interactions with other factors. Eventually other factors involved in targeting and folding, like the Signal Recognition Particle or cytosolic chaperones, must gain access to the nascent chain. AU. NAC preparations to date consist of two copurifying polypeptides. Here we rigorously show that these two polypeptides, termed alpha- and beta NAC, form a very stable complex in vivo and in vitro and that a functional complex can be reconstituted from the individual subunits. A dissection of the contributions of the individual subunits to NACs function revealed that both subunits are in direct contact with nascent polypeptide chains on the ribosome and that both contribute to the prevention of inappropriate interactions. However, beta NAC alone directly binds to the ribosome and is sufficient to prevent ribosome binding to the endoplasmic reticulum membrane.

关键词：氨基酸序列细胞系色谱法凝胶免疫组织化学分子监控蛋白类分子序列数据核酸类/代谢重组蛋白质类/化学重组蛋白质类/分离和提纯重组蛋白质类/代谢信号识别颗粒/代谢反式激活因子类/化学反式激活因子类/分离和提纯反式激活因子类/代谢动物狗小鼠

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Signal recognition particle components in the nucleolus

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2000年第1期97卷 55-60页

作者： Politz, JC Yarovoi, S Kilroy, SM Gowda, K Zwieb, C Pederson, T Univ Massachusetts Sch Med Dept Biochem & Mol Biol Worcester MA 01605 USA Univ Texas Ctr Hlth Dept Biol Mol Tyler TX 75708 USA

The signal recognition particle (SRP) is a ribonucleoprotein composed of an Alu domain and an S domain. The S domain contains unique sequence SRP RNA and four SRP proteins: SRP19, SRP54, SRP68, and SRP72. SRP interacts with ribosomes to bring translating membrane and secreted proteins to the endoplasmic reticulum (ER) for proper processing. Additionally, SRP RNA is a member of a family of small nonribosomal RNAs found recently in the nucleolus, suggesting that the nucleolus is more plurifunctional than previously realized. It was therefore of interest to determine whether other SRP components localize to this intranuclear site. In transfected rat fibroblasts, green fluorescent protein fusions of SRP19, SRP68, and SRP72 localized to the nucleolus, as well as to the cytoplasm, as expected. SRP68 also accumulated in the ER, consistent with its affinity for the ER-bound SRP receptor. SRP54 was detected in the cytoplasm as a green fluorescent protein fusion and in immunofluorescence studies, but was not detected in the nucleolus. In situ hybridization experiments also revealed endogenous SRP RNA in the nucleolus. These results demonstrate that SRP RNA and three SRP proteins visit the nucleolus, suggesting that partial SRP assembly, or another unidentified activity of the SRP components, occurs at the nucleolus. SRP54 apparently interacts with nascent SRP beyond the nucleolus, consistent with in vitro reconstitution experiments showing that SRP19 must bind to SRP RNA before SRP54 binds. Our findings support the notion that the nucleolus is the site of assembly and/or interaction between the family of ribonucleoproteins involved in protein synthesis, in addition to ribosomes themselves.

关键词：细胞系细胞核仁/代谢内质网/代谢荧光抗体技术绿色荧光蛋白质类原位杂交发光蛋白质类分子序列数据 RNA 核/代谢重组融合蛋白质类酿酒酵母蛋白质类信号识别颗粒/代谢转染动物人类大鼠

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Role of Sec61α in the regulated transfer of the ribosome-nascent chain complex from the signal recognition particle to the translocation channel

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CELL 2000年第3期100卷 333-343页

作者： Song, WQ Raden, D Mandon, EC Gilmore, R Univ Massachusetts Sch Med Dept Biochem & Mol Biol Worcester MA 01655 USA

Targeting of ribosome-nascent chain complexes to the translocon in the endoplasmic reticulum is mediated by the concerted action of the signal recognition particle (SRP) and the SRP receptor (SR). Ribosome-stripped microsomes were digested with proteases to sever cytoplasmic domains of SR alpha, SR beta, TRAM, and the Sec61 complex. We characterized protein translocation intermediates that accumulate when Sec61 alpha or SRP is inactivated by proteolysis. In the absence of a functional Sec61 complex, dissociation of SRP54 from the signal sequence is blocked. Experiments using SR proteoliposomes confirmed the assembly of a membrane-bound posttargeting intermediate. These results strongly suggest that the Sec61 complex regulates the GTP hydrolysis cycle of the SRP-SR complex at the stage of signal sequence dissociation from SRP54.

关键词：生物转运内质网糙面/代谢鸟苷三磷酸/代谢水解作用膜糖蛋白类/代谢膜蛋白质类/代谢微粒体/代谢模型生物学蛋白质生物合成蛋白分选信号/代谢受体胞质和核/代谢受体肽/代谢核糖体/代谢酿酒酵母蛋白质类信号识别颗粒/代谢动物狗

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Assembly of archaeal signal recognition particle from recombinant components

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NUCLEIC ACIDS RESEARCH 2000年第6期28卷 1365-1373页

作者： Bhuiyan, SH Gowda, K Hotokezaka, H Zwieb, C Univ Texas Hlth Sci Ctr Dept Mol Biol Tyler TX 75710 USA Mem Sloan Kettering Canc Ctr Cellular Biochem & Biophys Program New York NY 10021 USA

Signal recognition particle (SRP) takes part in protein targeting and secretion in all organisms. Searches for components of archaeal SRP in primary databases and completed genomes indicated that archaea possess only homologs of SRP RNA, and proteins SRP19 and SRP54, A recombinant SRP was assembled from cloned, expressed and purified components of the hyperthermophilic archaeon Archaeoglobus fulgidus. Recombinant Af-SRP54 associated with the signal peptide of bovine preprolactin translated in vitro, As in mammalian SRP, Af-SRP54 binding to Af-SRP RNA required protein Af-SRP19, although notable amounts bound in absence of Af-SRP19, Archaeoglobus fulgidus SRP proteins also bound to full-length SRP RNA of the archaeon Methanococcus jannaschii, to eukaryotic human SRP RNA, and to truncated versions which corresponded to the large domain of SRP, Dependence on SRP19 was most pronounced with components from the same species, Reconstitutions with heterologous components revealed a significant potential of human SRP proteins to bind to archaeal SRP RNAs. Surprisingly, *** SRP RNA bound to human SRP54M quantitatively in the absence of SRP19, This is the first report of reconstitution of an archaeal SRP from recombinantly expressed purified components, The results highlight structural and functional conservation of SRP assembly between archaea and eucarya.

关键词：闪烁古球菌/化学闪烁古球菌/遗传学氮呤类碱基序列克隆分子保守序列交联试剂甲烷球菌属/遗传学分子序列数据核酸构象催乳素/化学催乳素/遗传学催乳素/代谢蛋白质结合蛋白质生物合成蛋白质前体/化学蛋白质前体/遗传学蛋白质前体/代谢蛋白分选信号/遗传学蛋白分选信号/代谢 RNA/生物合成 RNA/化学 RNA/遗传学 RNA/代谢 RNA结合蛋白质类/化学 RNA结合蛋白质类/遗传学 RNA结合蛋白质类/分离和提纯 RNA结合蛋白质类/代谢重组蛋白质类/化学重组蛋白质类/遗传学重组蛋白质类/分离和提纯重组蛋白质类/代谢酿酒酵母蛋白质类信号识别颗粒/化学信号识别颗粒/遗传学信号识别颗粒/分离和提纯信号识别颗粒/代谢动物牛人类

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The signal recognition particle-targeting pathway does not necessarily deliver proteins to the Sec-translocase in Escherichia coli

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JOURNAL OF BIOLOGICAL CHEMISTRY 1999年第29期274卷 20068-20070页

作者： Cristóbal, S Scotti, P Luirink, J von Heijne, G de Gier, JWL Univ Stockholm Arrhenius Lab Dept Biochem S-10691 Stockholm Sweden Biocentrum Amsterdam Dept Microbiol NL-1081 HV Amsterdam Netherlands

ProW is an Escherichia coli inner membrane protein that consists of a 100-residue-long periplasmic N-terminal tail (N-tail) followed by seven closely spaced transmembrane segments. N-tail translocation presumably proceeds in a C-to-N-terminal direction and represents a poorly understood aspect of membrane protein biogenesis. Here, using an in vivo depletion approach, we show that N-tail translocation in a ProW derivative comprising the N-tail and the first transmembrane segment fused to the globular P2 domain of leader peptidase depends both on the bacterial signal recognition particle (SRP) and the Sec-translocase. Surprisingly, however, a deletion construct with only one transmembrane segment downstream of the N-tail can assemble properly even under severe depletion of SecE, a central component of the Sec-translocase, but not under SRP-depletion conditions. To our knowledge, this is the first demonstration that the SRP-targeting pathway does not necessarily deliver SRP-dependent inner membrane proteins to the Sec-translocase. The data further suggest that N-tail translocation can proceed in the absence of a functional Sec-translocase.

关键词： ATP结合匣式转运子/化学 ATP结合匣式转运子/代谢细菌蛋白质类生物转运大肠杆菌/酶学大肠杆菌蛋白质类膜蛋白质类/化学膜蛋白质类/代谢信号识别颗粒/代谢

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