The structure of the dynactin complex and its interaction with dynein - PubMed (original) (raw)

The structure of the dynactin complex and its interaction with dynein

Linas Urnavicius et al. Science. 2015.

Abstract

Dynactin is an essential cofactor for the microtubule motor cytoplasmic dynein-1. We report the structure of the 23-subunit dynactin complex by cryo-electron microscopy to 4.0 angstroms. Our reconstruction reveals how dynactin is built around a filament containing eight copies of the actin-related protein Arp1 and one of β-actin. The filament is capped at each end by distinct protein complexes, and its length is defined by elongated peptides that emerge from the α-helical shoulder domain. A further 8.2 angstrom structure of the complex between dynein, dynactin, and the motility-inducing cargo adaptor Bicaudal-D2 shows how the translational symmetry of the dynein tail matches that of the dynactin filament. The Bicaudal-D2 coiled coil runs between dynein and dynactin to stabilize the mutually dependent interactions between all three components.

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Figures

Fig. 1. Cryo-EM structure of dynactin

(A) A 4.0Å cryo-EM map of dynactin segmented and colored according to its components. (B) A density map of a β-strand and ADP molecule in Arp1-C. (C) A molecular model of dynactin. (D) 6.3Å cryo-EM map showing helices in the dynactin shoulder.

Fig. 2. Capping the dynactin filament

(A) The barbed end is capped by CapZαβ. (B) CapZαβ contains five positive residues (blue) which interact with four negative residues (orange) on Arp1. The equivalent loop in actin contains only one negative residue. (C) The short Arp11 subdomain-2 loop prevents further subunit addition to the bottom protofilament. (D) Arp11 caps the top protofilament by binding the subdomain-2 loop of Arp1-I and sterically blocking (asterisk) subsequent subunit binding. (E) The pointed end complex: p62 extends over Arp11 to touch β-actin-H. (F) p25 and p27 pack end-on to Arp11 as a continuation of the bottom protofilament.

Fig. 3. The architecture of the p150Glued projection and shoulder

(A) Schematic models of p150Glued. (B) An 8.6Å cryo-EM structure with a docked p150Glued projection, colored according to A. (C) Native mass spectrometry of dynactin reveals the mass of the intact complex. (D) Tandem MS confirms the subunit composition of the complex. (E) The shoulder contains two arms (red and blue) that emerge from a dimerization center (green) and end in hook and paddle domains. (F) The C-terminus of the p150Glued dimer enters the shoulder and splits into separate helices.

Fig. 4. Shoulder peptides coat and measure the dynactin filament

(A,B) Four extended regions (ER1-4) connect to the shoulder paddles. (C) ER1-2 cover the full length of the top Arp1 protofilament. (D) ER3-4 cover the bottom protofilament subunits Arp1-B,D&F, but not the β-actin-H subunit.

Fig. 5. The dynein tail and its interaction with dynactin and BICD2N

(A) Cartoon model of the dynein tail/dynactin/BICD2N complex (TDB). (B) An 8.2Å cryo-EM structure of TDB. (C) An N-terminal domain dimerizes the dynein heavy chain (DHC) elongated domains, which wrap round the dynein intermediate chain (DIC2). (D) Crystal structure of the S.cerevisiae DHC N-terminus (Dyn11-557 ). (E) The Dyn11-557 structure fits well into the cryo-EM map. (F) The translational symmetry of DHC chain-1 and 2 matches the dynactin filament. (G) Interaction of chain-1 with BICD2N and dynactin (asterisks). (H) The second interaction site of chain-1 with dynactin is solely mediated by BICD2N.

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The structure of the dynactin complex and its interaction with dynein - PubMed (original) (raw)