| 1. |
- Eberth, Alexander, et al.
(författare)
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A BAR domain-mediated autoinhibitory mechanism for RhoGAPs of the GRAF family
- 2009
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 417:1, s. 371-377
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Tidskriftsartikel (refereegranskat)abstract
- The BAR (Bin/amphiphysin/Rvs) domain defines an emerging superfamily of proteins implicated in fundamental biological processes by sensing and inducing membrane curvature. We identified a novel autoregulatory function for the BAR domain of two related GAPs' (GTPase-activating proteins) of the GRAF (GTPase regulator associated with focal adhesion kinase) subfamily. We demonstrate that the N-terminal fragment of these GAPs including the BAR domain interacts directly with the GAP domain and inhibits its activity. Analysis of various BAR and GAP domains revealed that the BAR domain-mediated inhibition of these GAPs' function is highly specific. These GAPs, in their autoinhibited state, are able to bind and tubulate liposomes in vitro, and to generate lipid tubules in cells. Taken together, we identified BAR domains as cis-acting inhibitory elements that very likely mask the active sites of the GAP domains and thus prevent down-regulation of Rho proteins. Most remarkably, these BAR proteins represent a dual-site system with separate membrane-tubulation and GAP-inhibitory functions that operate simultaneously.
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| 2. |
- Lundmark, Richard, et al.
(författare)
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The beta-appendages of the four adaptor-protein (AP) complexes: structure and binding properties, and identification of sorting nexin 9 as an accessory protein to AP-2
- 2002
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 362:3, s. 597-607
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Tidskriftsartikel (refereegranskat)abstract
- Adaptor protein (AP) complexes are essential components for the formation of coated vesicles and the recognition of cargo proteins for intracellular transport. Each AP complex exposes two appendage domains with that function to bind regulatory accessory proteins in the cytosol. Secondary structure predictions, sequence alignments and CD spectroscopy were used to relate the beta-appendages of all human AP complexes to the previously published crystal structure of AP-2. The results suggested that the beta-appendages of AP-1, AP-2 and AP-3 have similar structures, consisting of two subdomains, whereas that of AP-4 lacks the inner subdomain. Pull-down and overlay assays showed partial overlap in the binding specificities of the beta-appendages of AP-1 and AP-2, whereas the corresponding domain of AP-3 displayed a unique binding pattern. That AP-4 may have a truncated, non-functional domain was indicated by its apparent inability to bind any proteins from cytosol. Of several novel beta-appendage-binding proteins detected, one that had affinity exclusively for AP-2 was identified as sorting nexin 9 (SNX9). SNX9, which contains a phox and an Src homology 3 domain, was found in large complexes and was at least partially associated with AP-2 in the cytosol. SNX9 may function to assist AP-2 in its role at the plasma membrane.
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| 3. |
- Lundmark, Richard, et al.
(författare)
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Arf family GTP loading is activated by, and generates, positive membrane curvature.
- 2008
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Ingår i: The Biochemical journal. - 1470-8728. ; 414:2, s. 189-94
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Tidskriftsartikel (refereegranskat)abstract
- Small G-proteins belonging to the Arf (ADP-ribosylation factor) family serve as regulatory proteins for numerous cellular processes through GTP-dependent recruitment of effector molecules. In the present study we demonstrate that proteins in this family regulate, and are regulated by, membrane curvature. Arf1 and Arf6 were shown to load GTP in a membrane-curvature-dependent manner and stabilize, or further facilitate, changes in membrane curvature through the insertion of an amphipathic helix.
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