PDBsum entry 1c0f

Contractile protein

PDB id: 1c0f

Contents

Protein chains

127 a.a. *

368 a.a. *

Ligands

ATP

Metals

_CA ×3

Waters ×401

* Residue conservation analysis

PDB id:

1c0f

Name:

Contractile protein

Title:

Crystal structure of dictyostelium caatp-actin in complex with gelsolin segment 1

Structure:

Gelsolin segment 1. Chain: s. Engineered: yes. Mutation: yes. Actin. Chain: a

Source:

Homo sapiens. Human. Organism_taxid: 9606. Expressed in: escherichia coli. Expression_system_taxid: 562. Dictyostelium discoideum. Organism_taxid: 44689

Biol. unit:

Dimer (from PQS)

Resolution:

2.40Å R-factor: 0.183 R-free: 0.231

Authors:

Y.Matsuura,M.Stewart,M.Kawamoto,N.Kamiya,K.Saeki,T.Yasunaga, T.Wakabayashi

Key ref:

Y.Matsuura et al. (2000). Structural basis for the higher Ca(2+)-activation of the regulated actin-activated myosin ATPase observed with Dictyostelium/Tetrahymena actin chimeras. J Mol Biol, 296, 579-595. PubMed id: 10669610 DOI: 10.1006/jmbi.1999.3467

Date:

16-Jul-99 Release date: 01-Mar-00

Protein chain

P06396  (GELS_HUMAN) -  Gelsolin from Homo sapiens

Seq: 782 a.a.

Struc: 127 a.a.*

Protein chain

P07830  (ACT1_DICDI) -  Major actin from Dictyostelium discoideum

Seq: 376 a.a.

Struc: 368 a.a.*

* PDB and UniProt seqs differ at 5 residue positions (black crosses)

DOI no: 10.1006/jmbi.1999.3467

J Mol Biol 296:579-595 (2000)

PubMed id: 10669610

Structural basis for the higher Ca(2+)-activation of the regulated actin-activated myosin ATPase observed with Dictyostelium/Tetrahymena actin chimeras.

Y.Matsuura, M.Stewart, M.Kawamoto, N.Kamiya, K.Saeki, T.Yasunaga, T.Wakabayashi.

ABSTRACT

Replacement of residues 228-230 or 228-232 of subdomain 4 in Dictyostelium actin with the corresponding Tetrahymena sequence (QTA to KAY replacement: half chimera-1; QTAAS to KAYKE replacement: full chimera) leads to a higher Ca(2+)-activation of the regulated acto-myosin subfragment-1 ATPase activity. The ratio of ATPase activation in the presence of tropomyosin-troponin and Ca(2+) to that without tropomyosin-troponin becomes about four times as large as the ratio for the wild-type actin. To understand the structural basis of this higher Ca(2+)-activation, we have determined the crystal structures of the 1:1 complex of Dictyostelium mutant actins (half chimera-1 and full chimera) with gelsolin segment-1 to 2.0 A and 2.4 A resolution, respectively, together with the structure of wild-type actin as a control. Although there were local changes on the surface of the subdomain 4 and the phenolic side-chain of Tyr230 displaced the side-chain of Leu236 from a non-polar pocket to a more solvent-accessible position, the structures of the actin chimeras showed that the mutations in the 228-232 region did not introduce large changes in the overall actin structure. This suggests that residues near position 230 formed part of the tropomyosin binding site on actin in actively contracting muscle. The higher Ca(2+)-activation observed with A230Y-containing mutants can be understood in terms of a three-state model for thin filament regulation in which, in the presence of both Ca(2+) and myosin heads, the local changes of actin generated by the mutation (especially its phenolic side-chain) facilitate the transition of thin filaments from a "closed" state to an "open" state. Between 394 and 469 water molecules were identified in the different structures and it was found that actin recognizes hydrated forms of the adenine base and the Ca ion in the nucleotide binding site.

Selected figure(s)

Figure 2.
Figure 2. Overview of the crystal structure of the complex formed between wild-type Dictyostelium actin (yellow) and gelsolin segment 1 (light green). The ATP is shown as a ball-and-stick model and the calcium ions as orange spheres. Figure 2 and Figure 8 were prepared with the molecular graphics program MOLSCRIPT [Kraulis 1991].

Figure 7.
Figure 7. Schematic representation showing the interaction between Ca^2+ ATP and a mutant actin (half chimera-1). Water molecules (pink spheres) are important for mediating both the interaction between the adenine ring and actin and also for the binding of the Ca^2+ and phosphate. The adenine base fits in a hydrophobic pocket (yellow thick line) but many of its hydrogen-bonded interactions with polar groups on actin are mediated through water molecules. Similarly, the interactions of Ca^2+ to acidic residues on actin such as aspartate residues 11 and 154 are mediated through water molecules. Broken cyan lines correspond to hydrogen bonds or electrostatic interactions. The corresponding distances in Å are given next to the broken lines. The distance in Å between Wat203 and the g-phosphorous is also given next to a black arrow.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2000, 296, 579-595) copyright 2000.

Figures were selected by an automated process.