Crystal Structure of the α-Actinin Rod Reveals an Extensive Torsional Twist

AbstractBackground: α-Actinin is a ubiquitously expressed protein found in numerous actin structures. It consists of an N-terminal actin binding domain, a central rod domain, and a C-terminal domain and functions as a homodimer to cross-link actin filaments. The rod domain determines the distance between cross-linked actin filaments and also serves as an interaction site for several cytoskeletal and signaling proteins.Results: We report here the crystal structure of the α-actinin rod. The structure is a twisted antiparallel dimer that contains a conserved acidic surface.Conclusions: The novel features revealed by the structure allow prediction of the orientation of parallel and antiparallel cross-linked actin filaments in relation to α-actinin. The conserved acidic surface is a possible interaction site for several cytoplasmic tails of transmembrane proteins involved in the recruitment of α-actinin to the plasma membrane

Flexible Structure of Peptide-Bound Filamin A Mechanosensor Domain Pair 20-21

Filamins (FLNs) are large, multidomain actin cross-linking proteins with diverse functions. Besides regulating the actin cytoskeleton, they serve as important links between the extracellular matrix and the cytoskeleton by binding cell surface receptors, functioning as scaffolds for signaling proteins, and binding several other cytoskeletal proteins that regulate cell adhesion dynamics. Structurally, FLNs are formed of an amino terminal actin-binding domain followed by 24 immunoglobulin-like domains (IgFLNs). Recent studies have demonstrated that myosin-mediated contractile forces can reveal hidden protein binding sites in the domain pairs IgFLNa18-19 and 20-21, enabling FLNs to transduce mechanical signals in cells. The atomic structures of these mechanosensor domain pairs in the resting state are known, as well as the structures of individual IgFLN21 with ligand peptides. However, little experimental data is available on how interacting protein binding deforms the domain pair structures. Here, using small-angle x-ray scattering-based modelling, x-ray crystallography, and NMR, we show that the adaptor protein migfilin-derived peptide-bound structure of IgFLNa20-21 is flexible and adopts distinctive conformations depending on the presence or absence of the interacting peptide. The conformational changes reported here may be common for all peptides and may play a role in the mechanosensor function of the site.Peer reviewe

Psykoterapeuttikoulutuksia tutkimalla vaikuttavampaa opetusta ja hoitoa?

English summar

Molecular basis of filamin a-filGAP interaction and its impairment in congenital disorders associated with filamin a mutations

Peer reviewe

Binding Properties and Stability of the Ras-Association Domain of Rap1-GTP Interacting Adapter Molecule (RIAM)

The Rap1-GTP interacting adapter protein (RIAM) is an important protein in Rap1-mediated integrin activation. By binding to both Rap1 GTPase and talin, RIAM recruits talin to the cell membrane, thus facilitating talin-dependent integrin activation. In this article, we studied the role of the RIAM Ras-association (RA) and pleckstrin-homology (PH) domains in the interaction with Rap1. We found that the RA domain was sufficient for GTP-dependent interaction with Rap1B, and the addition of the PH domain did not change the binding affinity. We also detected GTP-independent interaction of Rap1B with the N-terminus of RIAM. In addition, we found that the PH domain stabilized the RA domain both in vitro and in cells

Kokemuksia ongelmaperusteisesta opiskelusta

nonPeerReviewe

Binding Properties and Stability of the Ras-Association Domain of Rap1-GTP Interacting Adapter Molecule (RIAM)

The Rap1-GTP interacting adapter protein (RIAM) is an important protein in Rap1-mediated integrin activation. By binding to both Rap1 GTPase and talin, RIAM recruits talin to the cell membrane, thus facilitating talin-dependent integrin activation. In this article, we studied the role of the RIAM Ras-association (RA) and pleckstrin-homology (PH) domains in the interaction with Rap1. We found that the RA domain was sufficient for GTP-dependent interaction with Rap1B, and the addition of the PH domain did not change the binding affinity. We also detected GTP-independent interaction of Rap1B with the N-terminus of RIAM. In addition, we found that the PH domain stabilized the RA domain both in vitro and in cells.peerReviewe

Logarithmic scattering curves as a function of momentum transfer (s).

<p>(<b>A</b>) Comparison of all the constructs studied. (<b>B</b>) Comparison of compact two-domain fragments with the average (FLNc10-11) and completely extended fragments (FLNc8-9). The curves are displaced on the Y-axis for clarity.</p

Summary of the results.

<p><b>Each panel</b> shows a monomer of FLN with ABD in red, followed by 24 Ig repeats and dimerization domain in blue. <b>Upper panel</b> shows previously known domain pairs in the Rod 2 region, FLN 16–17, 18–19 and 20–21 in lemon, purple and mustard, respectively. The domains that share high sequence similarity with pair forming domain 21 are highlighted with a star. <b>Middle panel</b> shows the recently revealed three-domain module in the Rod 1 region (Domain 3 in yellow, 4 in green and 5 in cyan). In addition, the arrangement of the three-domain pairs of the Rod 2 region is depicted. <b>Lower panel</b> shows the new candidates for inter-domain interactions revealed in this study.</p