Towards a Complete Atomic Structure of Spectrin Family Proteins

Broderick, Mike; Winder, Steven J.

doi:10.1006/jsbi.2002.4465

Cited by 50 publications

(38 citation statements)

References 67 publications

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“…In such cases, the larger peaks almost always occur before the smaller peaks. Such results contrast with findings of Li et al (20) for single titin chains of alternating I 27 and I 28 domains and are discussed in detail later. Total Unfolding Length and Peak Distribution AnalysisFour thousand tip-to-surface contacts were typically performed on ␣ϩ␤-spectrin heterodimers as well as on all of the two-and four-repeat ␣-and ␤-spectrin monomer constructs.…”

Section: Resultscontrasting

confidence: 58%

“…In both erythroid and non-erythroid systems, the N-terminal CH-domains of ␤-spectrin bind actin (27), and ␤-spectrin can also bind protein 4.1 into a highly stable ternary complex with F-actin (24). The EF-hands of ␣-spectrin might also enter into this complex (27) and effectively supplement the stress-sharing because of the strong lateral interaction between ␣ 21 and ␤ 1 repeats. When F-actin junctional complexes are separated, the ␣␤-tetramer that interconnects two adjacent complexes will be stressed by a force, F, that will generally be divided by the ␣-and ␤-chains.…”

Section: Forced Unfolding Of Heterodimersmentioning

confidence: 99%

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Influence of Lateral Association on Forced Unfolding of Antiparallel Spectrin Heterodimers

Law

Harper

Speicher

et al. 2004

Journal of Biological Chemistry

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Protein extensibility appears to be based broadly on conformational changes that can in principle be modulated by protein-protein interactions. Spectrin family proteins, with their extensible three-helix folds, enable evaluation of dimerization effects at the single molecule level by atomic force microscopy. Although some spectrin family members function physiologically only as homodimers (e.g. ␣-actinin) or are strictly monomers (e.g. dystrophin), ␣-and ␤-spectrins are stable as monomeric forms but occur physiologically as ␣,␤-heterodimers bound laterally lengthwise. For short constructs of ␣-and ␤-spectrin, either as monomers or as ␣,␤-dimers, sawtooth patterns in atomic force microscopy-forced extension show that unfolding stochastically extends repeats ϳ4 -5-fold greater in length than native conformations. For both dimers and monomers, distributions of unfolding lengths appear bimodal; major unfolding peaks reflect single repeats, and minor unfolding peaks at twice the length reflect tandem repeats. Cooperative unfolding thus propagates through helical linkers between serial repeats (1, 2). With lateral heterodimers, however, the force distribution is broad and shifted to higher forces. The associated chains in a dimer can stay together and unfold simultaneously in addition to unfolding independently. Weak lateral interactions do not inhibit unfolding, but strong lateral interactions facilitate simultaneous unfolding analogous to serial repeat coupling within spectrin family proteins.As cytoskeletal proteins, spectrin superfamily proteins play important roles in cell organization and membrane mechanics (3, 4). As flexible linkers that bind to actin filaments, these proteins function in both monomeric and associated forms. Erythroid ␣I-and ␤I-spectrin were the first identified spectrins among a still growing superfamily that includes ␣-actinin, dystrophin, utrophin, and many additional proteins that share homologous triple-helical repeat motifs (5). In the red cell, ␣-chains of 20 repeats associate antiparallel along their lengths with ␤-chains of 17 repeats. The association is nucleated near the N terminus of ␤-spectrin (6) that ends with an actin binding domain, which mediates formation of a cross-linked network (7). The ability of spectrin monomers to first dimerize laterally and then associate head-to-head as tetramers that cross-link actin is especially crucial to the resilience of the red cell membrane in circulation. Defects in association, for example, lead to membrane instabilities typical in hereditary pyropoikilocytosis (8). Like red cell spectrin, ␣-actinin, with its four homologous repeats, also associates laterally and cross-links actin, imparting stability to structures that range from focal adhesions to Z-lines of myotubes (5). Dystrophin and utrophin (5), in contrast, are hypothesized to impart cortical stability to diverse membranes as monomeric actin-binding proteins.For all of the spectrin family proteins, length and extensibility are deemed central to function. Surprisingly, perhaps, rec...

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Section: Resultscontrasting

confidence: 58%

Section: Forced Unfolding Of Heterodimersmentioning

confidence: 99%

Influence of Lateral Association on Forced Unfolding of Antiparallel Spectrin Heterodimers

Law

Harper

Speicher

et al. 2004

Journal of Biological Chemistry

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“…Erythrocyte spectrins associate with the plasma membrane both directly, through their PH domains and interactions with specific integral membrane proteins, and indirectly, through ankyrin. Erythrocyte spectrins interact with actin both directly and indirectly; these interactions are essential to membrane elasticity and stability [26][27][28].…”

Section: The Sec14p/spectrin Repeat Region Of Kalirin Affects Cell Momentioning

confidence: 99%

“…Gel filtration identified endogenous Kal7 in high molecular weight complexes. Since ΔKal7 does not exhibit this behavior, neither the Kal-GEF1/filamin A interaction [11], the Kal-PH1/TrkA interaction [26][27][28] nor interactions with PDZ binding domain proteins such as neurabin, ZO-1, ZO-2 and afadin [24] plays an essential role in it. Although Kal7 andΔKal7 may differ in the ability of their spectrin repeat regions to bind to integral membrane proteins like peptidylglycine Δ-amidating monooxygenase [12] and membrane associated proteins like Arf6-GDP [10], the dramatic differences observed in transfected cells indicate inherent differences in the properties of these two proteins.…”

Section: δKal7 Forms Soluble Dimers While Kal7 Forms Insoluble Oligomersmentioning

confidence: 99%

Autonomous functions for the Sec14p/spectrin-repeat region of Kalirin

Schiller

Ferraro

Wang

et al. 2008

Experimental Cell Research

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Kalirin is a GDP/GTP exchange factor (GEF) for Rho proteins that modulates the actin cytoskeleton in neurons. Alternative splicing generates Δ-isoforms, which encode the RhoGEF domain, but lack the N-terminal Sec14p domain and first 4 spectrin-like repeats of the full-length isoforms. Splicing has functional consequences, with Kal7 but not ΔKal7 causing formation of dendritic spines. Cells lacking endogenous Kalirin were used to explore differences between these splice variants. Expression of ΔKal7 in this system induces extensive lamellipodial sheets, while expression of Kal7 induces formation of adherent compact, round cells with abundant cortical actin. Based on in vitro and cell-based assays, Kal7 and ΔKal7 are equally active GEFs, suggesting that other domains are involved in controlling cell morphology. Catalytically inactive Kal7 and a Kalirin fragment which includes only Sec14p and spectrin-like domains retain the ability to produce compact, round cells and fractionate as high molecular weight complexes. Separating the Sec14p domain from the spectrin-like repeats eliminates the ability of Kal7 to cause this response. The isolated Sec14p domain binds PIP 2 (3,5) and PIP3, but does not alter cell morphology. We conclude that the Sec14p and Nterminal spectrin-like domains of Kalirin play critical roles in distinguishing the actions of full-length and Δ-Kalirin.

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“…Although there are no atomic resolution structures available for the STRs of dystrophin, numerous X-ray and NMR structures of homologous motifs from other members of the spectrin family are available [1,4], and it is now understood that these motifs adopt a triple α-helical bundle in which the three helices are arranged in a zig-zag fashion. This arrangement places the N and C-terminus at opposite ends of this bundle, and tandem arrangement of these motifs produces the long rod-shaped structures of these proteins.…”

Section: Introductionmentioning

confidence: 99%

Stability of dystrophin STR fragments in relation to junction helicity

Mirza

Menhart

2008

Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics

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Dystrophin is a rod shaped protein consisting of amino-and carboxy-terminal binding domains linked by a large central rod composed of 24 homologous copies of the STR motif and 4 nonhomologous regions termed hinges. These hinges are proposed to confer local flexibility; conversely, the tacit implication is that the STR regions away from the hinges are comparatively rigid. This, and the repeating nature of this rod, has contributed to the view that the STR region of the rod is uniform and monolithic. However, we have produced various 2 STR fragments, chosen to have high and low α-helix content at their junctions with each other, and show that they exhibit markedly different stabilities. In contrast to a related protein, spectrin, these differences are not correlated with the calculated helicity, but appear to be an intrinsic property of the motifs themselves. A full understanding of how these properties vary along the length of the rod has implications for the engineering of these rods regions in exon-skipping and mini-dystrophin therapies.

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Towards a Complete Atomic Structure of Spectrin Family Proteins

Cited by 50 publications

References 67 publications

Influence of Lateral Association on Forced Unfolding of Antiparallel Spectrin Heterodimers

Influence of Lateral Association on Forced Unfolding of Antiparallel Spectrin Heterodimers

Autonomous functions for the Sec14p/spectrin-repeat region of Kalirin

Stability of dystrophin STR fragments in relation to junction helicity

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