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- Title
A CapG gain-of-function mutant reveals critical structural and functional determinants for actin filament severing.
- Authors
Zhang, Y.; Vorobiev, Sergey M.; Gibson, Bruce G.; Binghua Hao; Sidhu, Gurjit S.; Mishra, Vishnu S.; Yarmola, Elena G.; Bubb, Michael R.; Almo, Steven C.; Southwick, Frederick S.
- Abstract
CapG is the only member of the gelsolin family unable to sever actin filaments. Changing amino acids 84-91 (severing domain) and 124-137 (WH2-containing segment) simultaneously to the sequences of gelsolin results in a mutant, CapG-sev, capable of severing actin filaments. The gain of severing function does not alter actin filament capping, but is accompanied by a higher affinity for monomeric actin, and the capacity to bind and sequester two actin monomers. Analysis of CapG-sev crystal structure suggests a more loosely folded inactive conformation than gelsolin, with a shorter S1-S2 latch. Calcium binding to S1 opens this latch and S1 becomes separated from a closely interfaced S2-S3 complex by an extended arm consisting of amino acids 118-137. Modeling with F-actin predicts that the length of this WH2-containing arm is critical for severing function, and the addition of a single amino acid (alanine or histidine) eliminates CapG-sev severing activity, confirming this prediction. We conclude that efficient severing utilizes two actin monomer-binding sites, and that the length of the WH2-containing segment is a critical functional determinant for severing.
- Subjects
ACTIN; AMINO acids; BINDING sites; MONOMERS; CRYSTALS; IMMUNOSPECIFICITY
- Publication
EMBO Journal, 2006, Vol 25, Issue 19, p4458
- ISSN
0261-4189
- Publication type
Article
- DOI
10.1038/sj.emboj.7601323