Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
2000-3-23
pubmed:databankReference
pubmed:abstractText
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:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0022-2836
pubmed:author
pubmed:copyrightInfo
Copyright 2000 Academic Press.
pubmed:issnType
Print
pubmed:day
18
pubmed:volume
296
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
579-95
pubmed:dateRevised
2009-11-19
pubmed:meshHeading
pubmed-meshheading:10669610-Actins, pubmed-meshheading:10669610-Adenosine Triphosphate, pubmed-meshheading:10669610-Amino Acid Sequence, pubmed-meshheading:10669610-Amino Acid Substitution, pubmed-meshheading:10669610-Animals, pubmed-meshheading:10669610-Binding Sites, pubmed-meshheading:10669610-Calcium, pubmed-meshheading:10669610-Crystallization, pubmed-meshheading:10669610-Crystallography, X-Ray, pubmed-meshheading:10669610-Dictyostelium, pubmed-meshheading:10669610-Enzyme Activation, pubmed-meshheading:10669610-Gelsolin, pubmed-meshheading:10669610-Humans, pubmed-meshheading:10669610-Models, Molecular, pubmed-meshheading:10669610-Molecular Sequence Data, pubmed-meshheading:10669610-Myosins, pubmed-meshheading:10669610-Protein Conformation, pubmed-meshheading:10669610-Rabbits, pubmed-meshheading:10669610-Recombinant Fusion Proteins, pubmed-meshheading:10669610-Structure-Activity Relationship, pubmed-meshheading:10669610-Tetrahymena, pubmed-meshheading:10669610-Tropomyosin, pubmed-meshheading:10669610-Troponin, pubmed-meshheading:10669610-Water
pubmed:year
2000
pubmed:articleTitle
Structural basis for the higher Ca(2+)-activation of the regulated actin-activated myosin ATPase observed with Dictyostelium/Tetrahymena actin chimeras.
pubmed:affiliation
Department of Physics, School of Science, University of Tokyo, Hongo 7-3-1, Tokyo, Bunkyo-ku, 113-0033, Japan.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't