2hf3

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spinqualitylabelsall models 2hf3, resolution 1.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal structure of monomeric Actin in the ADP bound state

Overview

Actin filament growth and disassembly, as well as affinity for, actin-binding proteins, is mediated by the nucleotide-bound state of the, component actin monomers. The structural differences between ATP-actin and, ADP-actin, however, remain controversial. We expressed a cytoplasmic actin, in Sf9 cells, which was rendered non-polymerizable by virtue of two point, mutations in subdomain 4 (A204E/P243K). This homogeneous monomer, called, AP-actin, was crystallized in the absence of toxins, binding proteins, or, chemical modification, with ATP or ADP at the active site. The two surface, mutations do not perturb the structure. Significant differences between, the two states are confined to the active site region and sensor loop. The, active site cleft remains closed in both states. Minor structural shifts, propagate from the active site toward subdomain 2, but dissipate before, reaching the DNase binding loop (D-loop), which remains disordered in both, the ADP and ATP states. This result contrasts with previous structures of, actin made monomeric by modification with tetramethylrhodamine, which show, formation of an alpha-helix at the distal end of the D-loop in the, ADP-bound but not the ATP-bound form (Otterbein, L. R., Graceffa, P., and, Dominguez, R. (2001) Science 293, 708-711). Our reanalysis of the, TMR-modified actin structures suggests that the nucleotide-dependent, formation of the D-loop helix may result from signal propagation through, crystal packing interactions. Whereas the observed nucleotide-dependent, changes in the structure present significantly different surfaces on the, exterior of the actin monomer, current models of the actin filament lack, any actin-actin interactions that involve the region of these key, structural changes.

About this Structure

2HF3 is a Single protein structure of sequence from Drosophila melanogaster with CA and ADP as ligands. Full crystallographic information is available from OCA.

Reference

Crystal structures of expressed non-polymerizable monomeric actin in the ADP and ATP states., Rould MA, Wan Q, Joel PB, Lowey S, Trybus KM, J Biol Chem. 2006 Oct 20;281(42):31909-19. Epub 2006 Aug 18. PMID:16920713

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