Structural highlights
Publication Abstract from PubMedThe Phactr family of PP1-binding proteins and the myocardin-related transcription factor family of transcriptional coactivators contain regulatory domains comprising three copies of the RPEL motif, a G-actin binding element. We report the structure of a Phactr1 G-actinRPEL domain complex. Three G-actins surround the crank-shaped RPEL domain forming a closed helical assembly. Their spatial relationship is identical to the RPEL-actins within the pentavalent MRTF G-actinRPEL domain complex, suggesting that conserved cooperative interactions between actinRPEL units organize the assembly. In the trivalent Phactr1 complex, each G-actinRPEL unit makes secondary contacts with its downstream actin involving distinct RPEL residues. Similar secondary contacts are seen in G-actinRPEL peptide crystals. Loss-of-secondary-contact mutations destabilize the Phactr1 G-actinRPEL assembly. Furthermore, actin-mediated inhibition of Phactr1 nuclear import requires secondary contact residues in the Phactr1 N-terminal RPEL-N motif, suggesting that it involves interaction of RPEL-N with the C-terminal assembly. Secondary actin contacts by actin-bound RPEL motifs thus govern formation of multivalent actinRPEL assemblies. Structures of the Phactr1 RPEL Domain and RPEL Motif Complexes with G-Actin Reveal the Molecular Basis for Actin Binding Cooperativity.,Mouilleron S, Wiezlak M, O'Reilly N, Treisman R, McDonald NQ Structure. 2012 Oct 2. pii: S0969-2126(12)00335-8. doi:, 10.1016/j.str.2012.08.031. PMID:23041370[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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