1C0G

CRYSTAL STRUCTURE OF 1:1 COMPLEX BETWEEN GELSOLIN SEGMENT 1 AND A DICTYOSTELIUM/TETRAHYMENA CHIMERA ACTIN (MUTANT 228: Q228K/T229A/A230Y/E360H)

Summary for 1C0G

• Entry DOI: 10.2210/pdb1c0g/pdb
• Related: 1C0F 1DEJ
• Descriptor: PROTEIN (GELSOLIN SEGMENT 1), PROTEIN (CHIMERIC ACTIN), CALCIUM ION, ... (5 entities in total)
• Functional Keywords: actin mutant, contractile protein
• Biological source: Homo sapiens (human); More
• Cellular location: Isoform 2: Cytoplasm, cytoskeleton. Isoform 1: Secreted: P06396; Cytoplasm, cytoskeleton: P07830
• Total number of polymer chains: 2
• Total formula weight: 56564.99

Authors

Matsuura, Y.,Stewart, M.,Kawamoto, M.,Kamiya, N.,Saeki, K.,Yasunaga, T.,Wakabayashi, T. (deposition date: 1999-07-16, release date: 2000-03-01, Last modification date: 2022-12-21)

Primary citation

Matsuura, Y.,Stewart, M.,Kawamoto, M.,Kamiya, N.,Saeki, K.,Yasunaga, T.,Wakabayashi, T.
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, 2000

PubMed 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.

PubMed: 10669610
DOI: 10.1006/jmbi.1999.3467

Experimental method

X-RAY DIFFRACTION (2 Å)