Experientia最新文献

Immunogenetics. 免疫遗传学。

Experientia Pub Date : 2005-01-01 DOI: 10.1007/BF01941288

K Bender

引用次数: 487

Allosteric proteins after thirty years: the binding and state functions of the neuronal alpha 7 nicotinic acetylcholine receptors. 三十年后的变构蛋白:神经元α - 7烟碱乙酰胆碱受体的结合和状态功能。

Experientia Pub Date : 1996-12-15 DOI: 10.1007/BF01952106

S J Edelstein, J P Changeux

{"title":"Allosteric proteins after thirty years: the binding and state functions of the neuronal alpha 7 nicotinic acetylcholine receptors.","authors":"S J Edelstein, J P Changeux","doi":"10.1007/BF01952106","DOIUrl":"https://doi.org/10.1007/BF01952106","url":null,"abstract":"A key statement of the 1965 Monod-Wyman-Changeux (MWC) model for allosteric proteins concerns the distinction between the ligand-binding function (Y) and the relevant state function (R). Sequential models predict overlapping behavior of the two functions. In contrast, a straightforward experimental consequence of the MWC model is that for an oligomeric protein the parameters which characterize the two functions should differ significantly. Two situations, where R > Y and the system is hyper-responsive or where R < Y and the system is hypo-responsive, have been encountered. Indeed, the hyper-responsive pattern was first observed for the enzyme aspartate transcarbamoylase, by comparing Y with R monitored by a change in sedimentation. Extensions of the theory to ligand-gated channels led to the suggestion that, on the one hand, hyper-responsive properties also occur with high-affinity mutants. On the other hand, native channels of the acetylcholine neuronal alpha 7 receptor and low-affinity mutants of the glycine receptor can be interpreted in terms of the hypo-responsive pattern. For the ligand-gated channels, whereas R is detected directly by ion flux, ligand binding has rarely been measured and the formation of desensitized states may complicate the analysis. However, stochastic models incorporating both binding and channel opening for single molecules predict differences that should be measurable with new experimental approaches, particularly fluorescence correlation spectroscopy.","PeriodicalId":12087,"journal":{"name":"Experientia","volume":"52 12","pages":"1083-90"},"PeriodicalIF":0.0,"publicationDate":"1996-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/BF01952106","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19948972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 20

In vitro systems in the study of peroxisomal protein import. 体外系统中过氧化物酶体蛋白进口的研究。

Experientia Pub Date : 1996-12-15 DOI: 10.1007/BF01952102

A Baker

引用次数: 3

The mitochondrial processing peptidase: function and specificity. 线粒体加工肽酶：功能和特异性。

Experientia Pub Date : 1996-12-15 DOI: 10.1007/BF01952105

P Luciano, V Géli

{"title":"The mitochondrial processing peptidase: function and specificity.","authors":"P Luciano, V Géli","doi":"10.1007/BF01952105","DOIUrl":"10.1007/BF01952105","url":null,"abstract":"Targeting signals of mitochondrial precursors are cleaved in the matrix during or after import by the mitochondrial processing peptidase (MPP). This enzyme consists of two nonidentical alpha- and beta-subunits each of molecular weight of about 50 kDa. In mammals and fungi, MPP is soluble in the matrix, whereas in plants the enzyme is part of the cytochrome bc1 complex. MPP is a metalloendopeptidase which has been classified as a member of the pitrilysin family on the basis of the HXXEHX76E zinc-binding motif present in beta-MPP. Both subunits of MPP are required for processing activity. The alpha-subunit of MPP, which probably recognizes a three-dimensional motif adopted by the presequence, presents the presequence to beta-MPP, which carries the catalytic active site. MPP acts as an endoprotease on chemically synthesized peptides corresponding to mitochondrial presequences. Matrix-targeting signals and MPP cleavage signals seem to be distinct, although the two signals may overlap within a given presequence. The structural element helix-turn-helix, that cleavable presequences adopt in a membrane mimetic environment, may be required for processing but is not sufficient for proteolysis. Binding of the presequence by alpha-MPP tolerates a high degree of mutations of the presequence. alpha-MPP may present a degenerated cleavage site motif to beta-MPP in an accessible conformation for processing. The conformation of mitochondrial presequences bound to MPP remains largely unknown.","PeriodicalId":12087,"journal":{"name":"Experientia","volume":"52 12","pages":"1077-82"},"PeriodicalIF":0.0,"publicationDate":"1996-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/BF01952105","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19948971","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 29

Vacuolar H(+)-ATPase: from mammals to yeast and back. 液泡H(+)- atp酶:从哺乳动物到酵母再返回。

Experientia Pub Date : 1996-12-15 DOI: 10.1007/BF01952108

N Nelson, D J Klionsky

{"title":"Vacuolar H(+)-ATPase: from mammals to yeast and back.","authors":"N Nelson, D J Klionsky","doi":"10.1007/BF01952108","DOIUrl":"https://doi.org/10.1007/BF01952108","url":null,"abstract":"Vacuolar H(+)-adenosine triphosphatase (V-ATPase) is composed of distinct catalytic (V1) and membrane (V0) sectors containing several subunits. The biochemistry of the enzyme was mainly studied in organelles from mammalian cells such as chromaffin granules and clathrin-coated vesicles. Subsequently, mammalian cDNAs and yeast genes encoding subunits of V-ATPase were cloned and sequenced. The sequence information revealed the relation between V- and F-ATPase that evolved from a common ancestor. The isolation of yeast genes encoding subunits of V-ATPase opened an avenue for molecular biology studies of the enzyme. Because V-ATPase is present in every known eukaryotic cell and provides energy for vital transport systems, it was anticipated that disruption of genes encoding V-ATPase subunits would be lethal. Fortunately, yeast cells can survive the absence of V-ATPase by 'drinking' the acidic medium. So far only yeast cells have been shown to be viable without an active V-ATPase. In contrast to yeast, mammalian cells may have more than one gene encoding each of the subunits of the enzyme. Some of these genes encode tissue- and/or organelle-specific subunits. Expression of these specific cDNAs in yeast cells may reveal their unique functions in mammalian cells. Following the route from mammals to yeast and back may prove useful in the study of many other complicated processes.","PeriodicalId":12087,"journal":{"name":"Experientia","volume":"52 12","pages":"1101-10"},"PeriodicalIF":0.0,"publicationDate":"1996-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/BF01952108","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19948974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 16

Translational control of endogenous and recoded nuclear genes in yeast mitochondria: regulation and membrane targeting. 酵母线粒体内源和重编码核基因的翻译控制:调控和膜靶向。

Experientia Pub Date : 1996-12-15 DOI: 10.1007/BF01952112

T D Fox

引用次数: 45

The plasma membrane calcium pump: recent developments and future perspectives. 质膜钙泵的研究进展及展望。

Experientia Pub Date : 1996-12-15 DOI: 10.1007/BF01952107

E Carafoli, E Garcia-Martin, D Guerini

引用次数: 35

Actin-, myosin- and ubiquitin-dependent endocytosis. 肌动蛋白、肌凝蛋白和泛素依赖的内吞作用。

Experientia Pub Date : 1996-12-15 DOI: 10.1007/BF01952099

H Riezman, A Munn, M I Geli, L Hicke

引用次数: 41

Polypeptide translocation machinery of the yeast endoplasmic reticulum. 酵母内质网多肽易位机制。

Experientia Pub Date : 1996-12-15 DOI: 10.1007/BF01952100

S K Lyman, R Schekman

{"title":"Polypeptide translocation machinery of the yeast endoplasmic reticulum.","authors":"S K Lyman, R Schekman","doi":"10.1007/BF01952100","DOIUrl":"https://doi.org/10.1007/BF01952100","url":null,"abstract":"Proteins enter the secretory pathway by two general routes. In one, the complete polypeptide is made in the cytoplasm and held in an incompletely folded state by chaperoning adenosine triphosphatases (ATPases) such as hsp70. In Saccharomyces cerevisiae, fully synthesized secretory precursors engage the endoplasmic reticulum (ER) membrane by interaction with a set of Sec proteins comprising the polypeptide translocation apparatus (Sec61p, Sec62p, Sec63p, Sec71p, Sec72p). Productive interaction requires displacement of hsp70 from the precursor, a reaction that is facilitated by Ydj1p, a homologue of the Escherichia coli DnaJ protein. Both DnaJ and Ydj1p regulate chaperone activity by stimulating the ATPase activity of their respective hsp70 partners (E. coli DnaK and S. cerevisiae Ssa1p, respectively). In the ER lumen, another hsp70 chaperone, BiP, binds ATP and interacts with the ER membrane via its contact with a peptide loop of Sec63p. This loop represents yet another DnaJ homologue in that it contains a region of approximately 70 residue similarity to the 'J box', the most conserved region of the DnaJ family of proteins. In the presence of ATP, under conditions in which BiP can bind to Sec63p, the secretory precursor passes from the cytosol into the lumen through a membrane channel formed by Sec61p. A second route to the membrane pore that is used by many other secretory precursors, particularly in mammalian cells, requires that the polypeptide engage the ER membrane as the nascent chain emerges from the ribosome. Such cotranslational translocation bypasses the need for certain Sec proteins, instead utilizing an alternate set of cytosolic and membrane factors that allows the nascent chain to be inserted directly into the Sec61p channel.","PeriodicalId":12087,"journal":{"name":"Experientia","volume":"52 12","pages":"1042-9"},"PeriodicalIF":0.0,"publicationDate":"1996-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/BF01952100","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"19949637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 14

The cytosolic and membrane components required for peroxisomal protein import. 过氧化物酶体蛋白输入所需的细胞质和膜组分。

Experientia Pub Date : 1996-12-15 DOI: 10.1007/BF01952101

S R Terlecky, W M Nuttley, S Subramani

引用次数: 4