Structure of the N-terminal half of gelsolin bound to actin: roles in severing, apoptosis and FAF (original) (raw)
Related papers
The Crystal Structure of Plasma Gelsolin: Implications for Actin Severing, Capping, and Nucleation
Cell, 1997
The structure of gelsolin has been determined by crystallography and comprises six structurally related domains that, in a Ca2+-free environment, pack together to form a compact globular structure in which the putative actin-binding sequences are not sufficiently exposed to enable binding to occur. We propose that binding Ca2+ can release the connections that join the N- and C-terminal halves of gelsolin, enabling each half to bind actin relatively independently. Domain shifts are proposed in response to Ca2+ as bases for models of how gelsolin acts to sever, cap, or nucleate F-actin filaments. The structure also invites discussion of polyphosphoinositide binding to segment 2 and suggests how mutation at Asp-187 could initiate a series of events that lead to deposition of amyloid plaques, as observed in victims of familial amyloidosis (Finnish type).
The gelsolin family of actin regulatory proteins: modular structures, versatile functions
FEBS Letters, 2003
This issue of FEBS Letters includes two manuscripts describing structural studies of gelsolin, the best-characterized member of a superfamily of actin binding proteins that sever, cap, and in some cases nucleate and bundle actin ¢laments. The manuscripts by Narayan et al. and Irobi et al. provide snapshots of gelsolin domains activated by calcium and in complex with the actin monomer, revealing new insights into the remarkable actin regulatory activities of this versatile protein. These studies build upon nearly a quarter of a century of research on gelsolin's e¡ects on actin dynamics and its role in normal and diseased cells. In the following minireview, we summarize the structural studies that have provided insights into gelsolin's severing and capping activities and look to the future of work on this remarkable molecule.
Determination of the gelsolin binding site on F-actin: implications for severing and capping
Gelsolin is a six-domain protein that regulates actin assembly by severing, capping, and nucleating filaments. We have used electron cryomicroscopy and helical reconstruction to identify its binding site on F-actin. To obtain fully decorated filaments under severing conditions, we have studied a derivative (G2-6) that has a reduced severing efficiency compared to gelsolin. A three-dimensional reconstruction of G2-6:F-actin was obtained by electron cryomicroscopy and helical reconstruction. The structure shows that gelsolin bridges two longitudinally associated monomers when it binds the filament. The F-actin binding region of G2-6 is centered axially at subdomain 3 and radially between subdomains 1 and 3 of the upper actin monomer. Our results suggest that for severing to occur, both gelsolin and actin undergo large conformational changes.
Grl~olin binds two monomers in the nucleating cumplca with Gtctin in calcium ml enpr uotin fil~mcnlx, Hc~wcvcr, 3 actin-binding dumuinr have been idcntiflcd within its 6 repenting acqucncc acynrenta carrcrponding to SI, U-3 and SJ-6. %I rnd S& 6 bind unly thetin wh~ct~ 52-3 bindr apcifically IO P-tlctin, Twu of'thc three domains (S&3 and S4.=6) arc required for nurlcetiun and tt diffcrcnr pair (SI and S2 ,,3) for rcvrrinp, Here WC show for the first fimc that the domains unique to nucleation (SJ;=6) or acvcring (SI) compete For the ~amc rcpion on r&domain I of Gaelin, WC further show thut S2-3 binds nctin tnotlomcrs weakly in GbufTer conditions and thaw rhis intcrrction pertiara when SI or S4-4 urc also boulld.
The Calcium Activation of Gelsolin: Insights from the 3Å Structure of the G4–G6/Actin Complex
Journal of Molecular Biology, 2002
Gelsolin participates in the reorganization of the actin cytoskeleton that is required during such phenomena as cell movement, cytokinesis, and apoptosis. It consists of six structurally similar domains, G1 -G6, which are arranged at resting intracellular levels of calcium ion so as to obscure the three actin-binding surfaces. Elevation of Ca 2þ concentrations releases latches within the constrained structure and produces large shifts in the relative positioning of the domains, permitting gelsolin to bind to and sever actin filaments. How Ca 2þ is able to activate gelsolin has been a major question concerning the function of this protein. We present the improved structure of the C-terminal half of gelsolin bound to monomeric actin at 3.0 Å resolution. Two classes of Ca 2þ -binding site are evident on gelsolin: type 1 sites share coordination of Ca 2þ with actin, while type 2 sites are wholly contained within gelsolin. This structure of the complex reveals the locations of two novel metal ion-binding sites in domains G5 and G6, respectively. We identify both as type 2 sites. The absolute conservation of the type 2 calcium-ligating residues across the six domains of gelsolin suggests that this site exists in each of the domains. In total, gelsolin has the potential to bind eight calcium ions, two type 1 and six type 2. The function of the type 2 sites is to facilitate structural rearrangements within gelsolin as part of the activation and actin-binding and severing processes. We propose the novel type 2 site in G6 to be the critical site that initiates overall activation of gelsolin by releasing the tail latch that locks calcium-free gelsolin in a conformation unable to bind actin.
The Calcium Activation of Gelsolin: Insights from the 3 � Structure of the G4�G6/Actin Complex
J Mol Biol, 2002
Gelsolin participates in the reorganization of the actin cytoskeleton that is required during such phenomena as cell movement, cytokinesis, and apoptosis. It consists of six structurally similar domains, G1–G6, which are arranged at resting intracellular levels of calcium ion so as to obscure the three actin-binding surfaces. Elevation of Ca2+ concentrations releases latches within the constrained structure and produces large shifts in the relative positioning of the domains, permitting gelsolin to bind to and sever actin filaments. How Ca2+ is able to activate gelsolin has been a major question concerning the function of this protein. We present the improved structure of the C-terminal half of gelsolin bound to monomeric actin at 3.0 Å resolution. Two classes of Ca2+-binding site are evident on gelsolin: type 1 sites share coordination of Ca2+ with actin, while type 2 sites are wholly contained within gelsolin. This structure of the complex reveals the locations of two novel metal ion-binding sites in domains G5 and G6, respectively. We identify both as type 2 sites. The absolute conservation of the type 2 calcium-ligating residues across the six domains of gelsolin suggests that this site exists in each of the domains. In total, gelsolin has the potential to bind eight calcium ions, two type 1 and six type 2. The function of the type 2 sites is to facilitate structural rearrangements within gelsolin as part of the activation and actin-binding and severing processes. We propose the novel type 2 site in G6 to be the critical site that initiates overall activation of gelsolin by releasing the tail latch that locks calcium-free gelsolin in a conformation unable to bind actin.