Acta physiologica Scandinavica. Supplementum最新文献_第3页

Structural aspects of transmembrane alpha-helices. 跨膜α -螺旋的结构方面。

Acta physiologica Scandinavica. Supplementum Pub Date : 1998-08-01

G von Heijne

引用次数: 0

Sorting of P-type ATPases in polarized epithelial cells. 极化上皮细胞中p型atp酶的分选。

Acta physiologica Scandinavica. Supplementum Pub Date : 1998-08-01

L A Dunbar, N Courtois-Coutry, D L Roush, T R Muth, C J Gottardi, V Rajendran, J Geibel, M Kashgarian, M J Caplan

{"title":"Sorting of P-type ATPases in polarized epithelial cells.","authors":"L A Dunbar, N Courtois-Coutry, D L Roush, T R Muth, C J Gottardi, V Rajendran, J Geibel, M Kashgarian, M J Caplan","doi":"","DOIUrl":"","url":null,"abstract":"The Na,K-ATPase and the H,K-ATPase are highly homologous members of the P-type family of ion transporting ATPase. Despite their structural similarity, these two pumps are sorted to different destinations in polarized epithelial cells. While the Na,K-ATPase is restricted to the basolateral surfaces of most epithelial cells types, the H,K-ATPase is concentrated at the apical plasmalemma and in a pre-apical vesicular storage compartment in the parietal cells of the stomach. We have generated molecular chimeras composed of complementary portions of these two pumps' alpha-subunits. By expressing these pump constructs in polarized epithelial cells in culture, we have been able to identify sequence domains which participate in the targetting of the holoenzyme. We find that information embedded within the sequence of the fourth transmembrane domain of the H,K-ATPase is sufficient to account for this protein's apical localization. Stimulation of gastric acid secretion results in insertion of the intracellular H,K-ATPase pool into the apical plasma membrane and inactivation of acid secretion is accompanied by the re-internalization of these pumps. We have identified a tyrosine-based signal in the cytoplasmic tail of the H,K-ATPase beta-subunit which appears to be required for this endocytosis. We have mutated the critical tyrosine residue to alanine and expressed the altered protein in transgenic mice. The H,K-ATPase remains continuously at the apical cell surface in parietal cells from these animals, and they constitutively hypersecrete gastric acid. These results demonstrate that the beta-subunit sequence mediates the internalization of the H,K-ATPase and is required for the cessation of gastric acid secretion. Thus, at least two sorting signals are required to ensure the proper targetting and regulation of the gastric H,K pump.","PeriodicalId":75414,"journal":{"name":"Acta physiologica Scandinavica. Supplementum","volume":"643 ","pages":"289-95"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20702419","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: 0

Yeast as an expression system for the study of P-glycoprotein and other ABC transporters. 酵母作为研究p -糖蛋白和其他ABC转运蛋白的表达系统。

Acta physiologica Scandinavica. Supplementum Pub Date : 1998-08-01

P Gros, L Beaudet, I L Urbatsch

引用次数: 0

Regulation of expression and function by subunits of oligomeric P-type ATPases. 寡聚p型atp酶亚基的表达和功能调控。

Acta physiologica Scandinavica. Supplementum Pub Date : 1998-08-01

P Béguin, U Hasler, A Beggah, K Geering

{"title":"Regulation of expression and function by subunits of oligomeric P-type ATPases.","authors":"P Béguin, U Hasler, A Beggah, K Geering","doi":"","DOIUrl":"","url":null,"abstract":"Na,K-ATPase activity must be finely controlled to meet the constantly changing physiological demands and to avoid destabilization of body homeostasis. Recent experimental evidence suggests that certain regulatory mechanisms are closely linked to the multisubunit structure of the Na,K-pump molecule. Na,K-ATPase is composed of a catalytic alpha and a glycoprotein beta subunit and sometimes of a third component, the gamma subunit. The beta subunit is a fundamental element of Na,K-ATPase in that its assembly in the ER is required for the structural and functional maturation of the catalytic alpha subunit and in consequence the beta subunit controls the expression of functional pumps at the cell surface. Furthermore, beta subunits influence the transport properties of the mature catalytic alpha subunits. Distinct interaction sites mediate the two functions of the beta subunit. Recently, we have started to characterize the gamma subunit, the functional role of which is yet not known. Immuno-radiolabeling of epitope-tagged gamma subunits expressed in Xenopus oocytes shows that the gamma subunits is a type I membrane protein which specifically associates only with Na,K-ATPase but not with other oligomeric P-type ATPases. The gamma peptide does not influence the formation or the cell surface expression of functional alpha-beta complexes. On the other hand, the gamma peptide itself needs association with Na,K-ATPase to be stably expressed and to be efficiently transported to the plasma membrane. Finally, the gamma subunit can modulate the K activation of Na,K-pumps. In conclusion, processes such as subunit assembly or the subunit composition of the cell surface expressed Na,K-pumps appear to cooperate with hormones in the control of the expression and the activity of Na,K-ATPase.","PeriodicalId":75414,"journal":{"name":"Acta physiologica Scandinavica. Supplementum","volume":"643 ","pages":"283-7"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20702418","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: 0

Structure-function relationships in transmembrane segments 4, 5, and 6 of the yeast plasma-membrane H(+)-ATPase. 酵母质膜H(+)- atp酶跨膜片段4,5和6的结构-功能关系。

Acta physiologica Scandinavica. Supplementum Pub Date : 1998-08-01

A Ambesi, N D Dewitt, V V Petrov, S Sen Gupta, C W Slayman

引用次数: 0

Molecular genetic probing of energy coupling by the yeast plasma membrane proton pump. 酵母质膜质子泵能量耦合的分子遗传学探测。

Acta physiologica Scandinavica. Supplementum Pub Date : 1998-08-01

P Soteropoulos, G Wang, D S Perlin

{"title":"Molecular genetic probing of energy coupling by the yeast plasma membrane proton pump.","authors":"P Soteropoulos, G Wang, D S Perlin","doi":"","DOIUrl":"","url":null,"abstract":"Genetic probing of PMA1, which encodes the plasma membrane H(+)-ATPase, has highlighted the putative role of the N-terminal half of the enzyme in the coupling process. Recent second-site suppressor studies indicate that significant interactions occur between the region near the site of phosphorylation, stalk segment 3 (S3), and the N-terminal transmembrane segments. Saturation mutagenesis was used to explore I183 in S2, which partially uncouples proton transport when converted to alanine. Numerous substitutions could be made at this position. However, stable substitutions with Arg, Tyr or Asn were often accompanied by second-site mutations at the extreme C-terminus, suggesting a close interaction between these regions. Several mutations in the putative stalk domain are known to alter coupling, and scanning glycine and proline mutagenesis was used to probe the predicted alpha-helical character of the stalk segments. The results indicate that the introduction of proline or glycine in S2, S4 or S5, was highly disruptive to enzyme function often resulting in cell death. Similar substitutions in stalk 3 yielded viable but significantly altered enzymes. These results suggest that the helical properties of these segments may be important for catalysis. Finally, the stalk region has been modeled as a helical bundle, which helps account for the effects of specific perturbations in this region.","PeriodicalId":75414,"journal":{"name":"Acta physiologica Scandinavica. Supplementum","volume":"643 ","pages":"115-22"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20701372","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: 0

Catalytic mechanism of P-glycoprotein. p -糖蛋白的催化机理。

Acta physiologica Scandinavica. Supplementum Pub Date : 1998-08-01

A E Senior

{"title":"Catalytic mechanism of P-glycoprotein.","authors":"A E Senior","doi":"","DOIUrl":"","url":null,"abstract":"We generated Chinese hamster ovary cells which are highly multidrug-resistant by selection in colchicine. Purified plasma membranes from these cells are enriched in P-glycoprotein (Pgp), up to 32% w/w of membrane protein. From plasma membranes we purified Pgp to homogeneity and reconstituted it in proteoliposomes. Both plasma membranes and purified reconstituted Pgp show drug-stimulated ATPase activity (approximately 20 s-1), comparable to other transport ATPases. These materials enable investigation and characterization of the catalytic sites and mechanism. Various approaches have been used, notably enzyme kinetics, photoaffinity and other covalent labelling, use of vanadate as transition-state analog, and inhibition by beryllium and aluminum fluoride. Both Pgp nucleotide sites hydrolyse MgATP and are of relatively low specificity and affinity for nucleotides. Trapping of nucleotide by vanadate in either site blocks catalysis at both sites; covalent inactivation of either site completely blocks turnover. Therefore the catalytic sites interact strongly, and it appears that when one site enters the transition-state conformation the other site is prohibited from doing so. A minimal reaction scheme for ATP hydrolysis has been determined. We have proposed an alternating catalytic sites scheme, in which drug-transport is coupled to relaxation of a high chemical potential conformation of the catalytic site (Pgp.MgADP.Pi) which is generated by the hydrolysis step itself. Photoaffinity labelling of Pgp catalytic sites has revealed equivalent Tyr residues which lie close to the adenine ring of bound MgATP in both sites.","PeriodicalId":75414,"journal":{"name":"Acta physiologica Scandinavica. Supplementum","volume":"643 ","pages":"213-8"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20701894","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: 0

Structure/function studies on the lactose permease of Escherichia coli. 大肠杆菌乳糖渗透酶的结构/功能研究。

Acta physiologica Scandinavica. Supplementum Pub Date : 1998-08-01

H R Kaback

引用次数: 0

The inventory of all ion and drug ATPases encoded by the yeast genome. 酵母基因组编码的所有离子和药物三磷酸腺苷酶的清单。

Acta physiologica Scandinavica. Supplementum Pub Date : 1998-08-01

A Goffeau

引用次数: 0

Metal-catalysed cleavage of Na,K-ATPase as a tool for study of structure-function relations. 金属催化裂解Na, k - atp酶作为研究结构-功能关系的工具。

Acta physiologica Scandinavica. Supplementum Pub Date : 1998-08-01

R Goldshleger, M Bar Shimon, E Or, S J Karlish

{"title":"Metal-catalysed cleavage of Na,K-ATPase as a tool for study of structure-function relations.","authors":"R Goldshleger, M Bar Shimon, E Or, S J Karlish","doi":"","DOIUrl":"","url":null,"abstract":"This paper describes a novel technique for specific cleavage of renal Na/K-ATPase, based on bound transition metal ions. The approach might have application to other P-type pumps or membrane proteins. In one type of experiment, specific cleavages of the alpha subunit have been observed following incubation with ascorbate plus H2O2. Five fragments with intact C-terminals and complementary fragments with intact N-terminals are detectable. The beta subunit is not cleaved. Cleavages depend on the presence of contaminant or added submicromolar concentrations of Fe2+ ions. The results suggest that Fe2+ (or Fe3+) binds with high affinity at the cytoplasmic surface and catalyze cleavages of peptide bonds close to the Fe2+ (or Fe3+) ion. The rate of cleavage is greatly affected by the conformational state of the protein, E1Na or E2(Rb), respectively. The findings provide information on spatial organization of the protein and suggest that the highly conserved regions of the alpha subunit, within the minor and major cytoplasmic loops, interact in the E2 or E2(Rb) conformations, but move apart in the E1 or E1Na conformations. In a second application of this technique, added Cu2+ ions at micromolar concentrations, have been shown to catalyse specific cleavages of both alpha and beta subunits at the extracellular surface. The experiments provide evidence for trans-membrane topology and proximity between trans-membrane segments M5-M10 within the alpha subunit and for interacting segments of alpha and beta subunits. We discuss the implications of metal-catalysed cleavages for spatial organisation of transmembrane helices of the protein.","PeriodicalId":75414,"journal":{"name":"Acta physiologica Scandinavica. Supplementum","volume":"643 ","pages":"89-97"},"PeriodicalIF":0.0,"publicationDate":"1998-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20701369","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: 0