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Tetramer

About: Tetramer is a research topic. Over the lifetime, 3658 publications have been published within this topic receiving 128346 citations.


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ComponentDOI
06 Jan 1989-Science
TL;DR: Comparison of the refined crystal structures of apo and a streptavidin:biotin complex shows that the high affinity results from several factors, including the formation of multiple hydrogen bonds and van der Waals interactions between biotin and the protein.
Abstract: The high affinity of the noncovalent interaction between biotin and streptavidin forms the basis for many diagnostic assays that require the formation of an irreversible and specific linkage between biological macromolecules. Comparison of the refined crystal structures of apo and a streptavidin:biotin complex shows that the high affinity results from several factors. These factors include the formation of multiple hydrogen bonds and van der Waals interactions between biotin and the protein, together with the ordering of surface polypeptide loops that bury the biotin in the protein interior. Structural alterations at the biotin binding site produce quaternary changes in the streptavidin tetramer. These changes apparently propagate through cooperative deformations in the twisted beta sheets that link tetramer subunits.

1,111 citations

Journal ArticleDOI
01 Sep 2011-Nature
TL;DR: It is proposed that destabilization of the helically folded tetramer precedes α-synuclein misfolding and aggregation in Parkinson’s disease and other human synucleinopathies, and that small molecules that stabilize the physiological tetramer could reduce α- Synuclein pathogenicity.
Abstract: Pathogenic aggregation of α-synuclein (αSyn) is implicated in Parkinson's disease and related disorders. αSyn has long been regarded as a natively unfolded monomer that acquires secondary structure only when it binds to its target. This model is the basis for a number of published studies, but Bartels et al. report that endogenous αSyn isolated under entirely non-denaturing conditions from brain tissue, cell lines and living human cells occurs principally as a folded tetramer. This finding suggests that destabilization of the αSyn tetramer precedes misfolding and aggregation in synucleinopathies, and that agents that stabilize the normal tetramer may reduce αSyn pathogenicity. Parkinson’s disease is the second most common neurodegenerative disorder1,2. Growing evidence indicates a causative role of misfolded forms of the protein α-synuclein in the pathogenesis of Parkinson’s disease3,4. Intraneuronal aggregates of α-synuclein occur in Lewy bodies and Lewy neurites5, the cytopathological hallmarks of Parkinson’s disease and related disorders called synucleinopathies4. α-Synuclein has long been defined as a ‘natively unfolded’ monomer of about 14 kDa (ref. 6) that is believed to acquire α-helical secondary structure only upon binding to lipid vesicles7. This concept derives from the widespread use of recombinant bacterial expression protocols for in vitro studies, and of overexpression, sample heating and/or denaturing gels for cell culture and tissue studies. In contrast, we report that endogenous α-synuclein isolated and analysed under non-denaturing conditions from neuronal and non-neuronal cell lines, brain tissue and living human cells occurs in large part as a folded tetramer of about 58 kDa. Several methods, including analytical ultracentrifugation, scanning transmission electron microscopy and in vitro cell crosslinking confirmed the occurrence of the tetramer. Native, cell-derived α-synuclein showed α-helical structure without lipid addition and had much greater lipid-binding capacity than the recombinant α-synuclein studied heretofore. Whereas recombinantly expressed monomers readily aggregated into amyloid-like fibrils in vitro, native human tetramers underwent little or no amyloid-like aggregation. On the basis of these findings, we propose that destabilization of the helically folded tetramer precedes α-synuclein misfolding and aggregation in Parkinson’s disease and other human synucleinopathies, and that small molecules that stabilize the physiological tetramer could reduce α-synuclein pathogenicity.

1,090 citations

Book ChapterDOI
TL;DR: This chapter discusses the fundamental molecular properties of avidin and streptavidin, which have been cloned and sequenced with the ultimate objective of using it in general expression systems for detecting and isolating fusion proteins.
Abstract: Publisher Summary This chapter discusses the fundamental molecular properties of avidin and streptavidin. Carbohydrate-free avidin can be obtained by use of deglycosylating enzymes and it has been shown to be present in significant amounts in some commercial preparations from which it may be separated by use of lectin columns. Improvement on the original use of biotinyl cellulose came with the introduction of iminobiotinyl derivatives of Sepharose that utilized the pH dependence of the binding 24 to achieve efficient elution. In iminobiotin, the ureido group becomes a guanidinium group; the form in which this is uncharged is strongly bound. The gene for streptavidin has been cloned and sequenced with the ultimate objective of using it in general expression systems for detecting and isolating fusion proteins. The stability is greatly enhanced by biotin binding, because the total free energy of binding is about 330 kJ/mol of tetramer. The dissociation constant for biotin is so low that it can be estimated only from the ratio of the rate constants for binding and exchange. The binding is accompanied by a red shift of the tryptophan spectrum and by a decrease in fluorescence, either of which can be used as the basis for quantitative assays.

996 citations

Journal ArticleDOI
05 May 1983-Nature
TL;DR: The tetrameric enzyme has circular 4-fold symmetry stabilized in part by metal ions bound on the symmetry axis, and sugar residues are attached to four of the five potential glycosylation sequences, and in one case contribute to the interaction between subunits in the tetramer.
Abstract: The influenza virus neuraminidase glycoprotein is a tetramer with a box-shaped head, 100 X 100 X 60 A, attached to a slender stalk. The three-dimensional structure of neuraminidase heads shows that each monomer is composed of six topologically identical beta-sheets arranged in a propeller formation. The tetrameric enzyme has circular 4-fold symmetry stabilized in part by metal ions bound on the symmetry axis. Sugar residues are attached to four of the five potential glycosylation sequences, and in one case contribute to the interaction between subunits in the tetramer.

869 citations

Journal ArticleDOI
13 Jul 1968-Nature
TL;DR: The structure of the contacts between unlike subunits suggests that the tetramer, rather than the αβ dimer, is the functional unit of haemoglobin.
Abstract: The secondary structure of the haemoglobin chains is similar to that of myoglobin, but some of the helical segments are more irregular and some parts of the non-helical segments have different conformations. The structure of the contacts between unlike subunits suggests that the tetramer, rather than the αβ dimer, is the functional unit of haemoglobin.

847 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023117
2022250
202144
202059
201957
201888