Structural basis of actin sequestration by thymosin-beta4: implications for WH2 proteins.Irobi, E., Aguda, A.H., Larsson, M., Guerin, C., Yin, H.L., Burtnick, L.D., Blanchoin, L., Robinson, R.C.
(2004) EMBO J 23: 3599-3608
- PubMed: 15329672
- DOI: https://doi.org/10.1038/sj.emboj.7600372
- Primary Citation of Related Structures:
- PubMed Abstract:
The WH2 (Wiscott-Aldridge syndrome protein homology domain 2) repeat is an actin interacting motif found in monomer sequestering and filament assembly proteins. We have stabilized the prototypical WH2 family member, thymosin-beta4 (Tbeta4), with respect to actin, by creating a hybrid between gelsolin domain 1 and the C-terminal half of Tbeta4 (G1-Tbeta4). This hybrid protein sequesters actin monomers, severs actin filaments and acts as a leaky barbed end cap. Here, we present the structure of the G1-Tbeta4:actin complex at 2 A resolution. The structure reveals that Tbeta4 sequesters by capping both ends of the actin monomer, and that exchange of actin between Tbeta4 and profilin is mediated by a minor overlap in binding sites. The structure implies that multiple WH2 motif-containing proteins will associate longitudinally with actin filaments. Finally, we discuss the role of the WH2 motif in arp2/3 activation.
Department of Medical Biochemistry and Microbiology, Uppsala Biomedical Center, Uppsala University, Uppsala, Sweden.