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  Structural and functional characterization of human Iba proteins

Schulze, J. O., Quedenau, C., Roske, Y., Adam, T., Schüler, H., Behlke, J., et al. (2008). Structural and functional characterization of human Iba proteins. FEBS Journal, 275(18), 4627-4640. doi:10.1111/j.1742-4658.2008.06605.x.

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Schulze, Jörg O., Author
Quedenau, Claudia1, Author              
Roske, Yvette, Author
Adam, Thomas, Author
Schüler, Herwig, Author
Behlke, Joachim, Author
Turnbull, Andrew P., Author
Sievert, Volker2, Author              
Scheich, Christoph3, Author
Mueller, Uwe, Author
Heinemann, Udo, Author
Büssow, Konrad2, Author              
Affiliations:
1Independent Junior Research Groups (OWL), Max Planck Institute for Molecular Genetics, Max Planck Society, ou_1433554              
2Dept. of Vertebrate Genomics (Head: Hans Lehrach), Max Planck Institute for Molecular Genetics, Max Planck Society, ou_1433550              
3Max Planck Society, ou_persistent13              

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Free keywords: Actin cross-linking, Allograft inflammatory factor 1, Calcium binding, EF-hand, Ionized calcium binding adapter molecule
 Abstract: Iba2 is a homolog of ionized calcium-binding adapter molecule 1 (Iba1), a 17-kDa protein that binds and cross-links filamentous actin (F-actin) and localizes to membrane ruffles and phagocytic cups. Here, we present the crystal structure of human Iba2 and its homodimerization properties, F-actin cross-linking activity, cellular localization and recruitment upon bacterial invasion in comparison with Iba1. The Iba2 structure comprises two central EF-hand motifs lacking bound Ca2+. Iba2 crystallized as a homodimer stabilized by a disulfide bridge and zinc ions. Analytical ultracentrifugation revealed a different mode of dimerization under reducing conditions that was independent of Ca2+. Furthermore, no binding of Ca2+ up to 0.1 mm was detected by equilibrium dialysis. Correspondingly, Iba EF-hand motifs lack residues essential for strong Ca2+ coordination. Sedimentation experiments and microscopy detected pronounced, indistinguishable F-actin binding and cross-linking activity of Iba1 and Iba2 with induction of F-actin bundles. Fluorescent Iba fusion proteins were expressed in HeLa cells and co-localized with F-actin. Iba1 was recruited into cellular projections to a larger extent than Iba2. Additionally, we studied Iba recruitment in a Shigella invasion model that induces cytoskeletal rearrangements. Both proteins were recruited into the bacterial invasion zone and Iba1 was again concentrated slightly higher in the cellular extensions.

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Language(s): eng - English
 Dates: 2008-09
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
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Title: FEBS Journal
Source Genre: Journal
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Pages: - Volume / Issue: 275 (18) Sequence Number: - Start / End Page: 4627 - 4640 Identifier: ISSN: 1742-464X