Localization and Structure of the Ankyrin-binding Site on 2-Spectrin

Department of Cell Biology and Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 03/2009; 284(11):6982-7. DOI: 10.1074/jbc.M809245200
Source: PubMed


Spectrins are tetrameric actin-cross-linking proteins that form an elastic network, termed the membrane skeleton, on the cytoplasmic surface of cellular membranes. At the plasma membrane, the membrane skeleton provides essential support, preventing loss of membrane material to environmental shear stresses. The skeleton also controls the location, abundance, and activity of membrane proteins that are critical to cell and tissue function. The ability of the skeleton to modulate membrane stability and function requires adaptor proteins that bind the skeleton to membranes. The principal adaptors are the ankyrin proteins, which bind to the beta-subunit of spectrin and to the cytoplasmic domains of numerous integral membrane proteins. Here, we present the crystal structure of the ankyrin-binding domain of human beta2-spectrin at 1.95 A resolution together with mutagenesis data identifying the binding surface for ankyrins on beta2-spectrin.

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Available from: Diana R. Tomchick, Aug 26, 2014
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    • "Not surprisingly, the I-TASSER threading procedure identified spectrin repeats as the best structural templates for all the tandem repeats, specifically 1CUN (chicken-brain -spectrin repeat R16-17) (Grum et al., 1999), 1U4Q (chicken-brain -spectrin repeat R15-17) (Kusunoki et al., 2004b), 1S35 (erythroid β-spectrin R8-9) (Kusunoki et al., 2004a), 3EDV (β2-spectrin repeat R14-16) (Davis et al., 2009) and 1F57 (erythrocyte ß-spectrin R14-15) (Ipsaro et al., 2009). As shown above, the identity score was very low, ranging between 0.08 and 0.18. "
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    ABSTRACT: The spectrin superfamily is composed of proteins involved in cytolinker functions. Their main structural feature is a large central subdomain with numerous repeats folded in triple helical coiled-coils. Their similarity of sequence was considered to be low without detailed quantification of the intra- and intermolecular levels. Among the superfamily, we considered as essential to propose an overview of the surface properties of all the repeats of the five proteins of the spectrin family, namely α- and β-spectrins, α-actinin, dystrophin and utrophin. Therefore, the aim of this work was to obtain a quantitative comparison of all the repeats at both the primary sequence and the three-dimensional levels. For that purpose, we applied homology modelling methods to obtain structural models for successive and overlapping tandem repeats of the human erythrocyte α- and β-spectrins and utrophin, as previously undertaken for dystrophin, and we used the known structure of α-actinin. The matrix calculation of the pairwise similarities of all the repeat sequences and the electrostatic and hydrophobic surface properties throughout the protein family support the view that spectrins and α-actinin on one hand and utrophin and dystrophin on the other hand share some structural similarities, but a detailed molecular characterisation highlights substantial differences. The repeats within the family are far from identical, which is consistent with their multiple interactions with different cellular partners, including proteins and membrane lipids.
    Journal of Structural Biology 03/2014; 186(3). DOI:10.1016/j.jsb.2014.03.011 · 3.23 Impact Factor
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    • "Although we currently have no direct evidence to support that these interactions have bona fide effects on the HIV-1 life cycle, it is tempting to speculate that such interactions may provide some possible mechanisms by which SPTBN1 may facilitate efficient reverse transcription . SPTBN1, with the N-terminal, actin-binding domain, has been implicated to serve as a scaffold protein for actin cytoskeleton (Hartwig, 1994; Davis et al., 2009). In fact, we have validated that SPTBN1 is required to maintain actin cytoskeletal structure in macrophages. "
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    ABSTRACT: The susceptibility of macrophages to HIV-1 infection is modulated during monocyte differentiation. IL-27 is an anti-HIV cytokine that also modulates monocyte activation. In this study, we present new evidence that IL-27 promotes monocyte differentiation into macrophages that are nonpermissive for HIV-1 infection. Although IL-27 treatment does not affect expression of macrophage differentiation markers or macrophage biological functions, it confers HIV resistance by down-regulating spectrin β nonerythrocyte 1 (SPTBN1), a required host factor for HIV-1 infection. IL-27 down-regulates SPTBN1 through a TAK-1-mediated MAPK signaling pathway. Knockdown of SPTBN1 strongly inhibits HIV-1 infection of macrophages; conversely, overexpression of SPTBN1 markedly increases HIV susceptibility of IL-27-treated macrophages. Moreover, we demonstrate that SPTBN1 associates with HIV-1 gag proteins. Collectively, our results underscore the ability of IL-27 to protect macrophages from HIV-1 infection by down-regulating SPTBN1, thus indicating that SPTBN1 is an important host target to reduce HIV-1 replication in one major element of the viral reservoir.
    Journal of Experimental Medicine 03/2013; 210(3). DOI:10.1084/jem.20120572 · 12.52 Impact Factor
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    • "Not surprisingly, the I-TASSER threading procedure identified spectrin repeats as the best templates, specifically 1U4Q (chicken-brain α-spectrin repeat R15-17) [14], 1S35 (erythroid β-spectrin R8-9) [13] and 3EDV (β2-spectrin repeat R14-16) [15]. As expected for spectrin-like repeats, the identity score was low, ranging between 0.08 and 0.18. "
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    ABSTRACT: Dystrophin is a large protein involved in the rare genetic disease Duchenne muscular dystrophy (DMD). It functions as a mechanical linker between the cytoskeleton and the sarcolemma, and is able to resist shear stresses during muscle activity. In all, 75% of the dystrophin molecule consists of a large central rod domain made up of 24 repeat units that share high structural homology with spectrin-like repeats. However, in the absence of any high-resolution structure of these repeats, the molecular basis of dystrophin central domain's functions has not yet been deciphered. In this context, we have performed a computational study of the whole dystrophin central rod domain based on the rational homology modeling of successive and overlapping tandem repeats and the analysis of their surface properties. Each tandem repeat has very specific surface properties that make it unique. However, the repeats share enough electrostatic-surface similarities to be grouped into four separate clusters. Molecular dynamics simulations of four representative tandem repeats reveal specific flexibility or bending properties depending on the repeat sequence. We thus suggest that the dystrophin central rod domain is constituted of seven biologically relevant sub-domains. Our results provide evidence for the role of the dystrophin central rod domain as a scaffold platform with a wide range of surface features and biophysical properties allowing it to interact with its various known partners such as proteins and membrane lipids. This new integrative view is strongly supported by the previous experimental works that investigated the isolated domains and the observed heterogeneity of the severity of dystrophin related pathologies, especially Becker muscular dystrophy.
    PLoS ONE 08/2011; 6(8):e23819. DOI:10.1371/journal.pone.0023819 · 3.23 Impact Factor
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