title: Actin-latrunculin A structure and function. Differential modulation of actin-binding protein function by latrunculin A.
abstract: Latrunculin A is used extensively as an agent to sequester monomeric actin in living cells. We hypothesize that additional activities of latrunculin A may be important for its biological activity. Our data are consistent with the formation of a 1:1 stoichiometric complex with an equilibrium dissociation constant of 0.2 to 0.4 micrometer and provide no evidence that the actin-latrunculin A complex participates in the elongation of actin filaments. Profilin and latrunculin A bind independently to actin, whereas binding of thymosin beta(4) to actin is inhibited by latrunculin A. Potential implications of this differential effect on actin-binding proteins are discussed. From a structural perspective, if latrunculin A binds to actin at a site that sterically influences binding by thymosin beta(4), then the observation that latrunculin A inhibits nucleotide exchange on actin implies an allosteric effect on the nucleotide binding cleft. Alternatively, if, as previously postulated, latrunculin A binds in the nucleotide cleft of actin, then its ability to inhibit binding by thymosin beta(4) is a surprising result that suggests that significant allosteric changes affect the thymosin beta(4) binding site. We show that latrunculin A and actin form a crystalline structure with orthorhombic space group P2(1)2(1)2(1) and diffraction to 3.10 A. A high resolution structure with optimized crystallization conditions should provide insight regarding these remarkable allosteric properties.
authors.affiliation: Department of Medicine, University of Florida, Gainesville, Florida 32610, USA.
authors.forename: E G
authors.initials: EG
authors.lastname: Yarmola
authors.forename: T
authors.initials: T
authors.lastname: Somasundaram
authors.forename: T A
authors.initials: TA
authors.lastname: Boring
authors.forename: I
authors.initials: I
authors.lastname: Spector
authors.forename: M R
authors.initials: MR
authors.lastname: Bubb
mesh_terms: D000199:Actins / Q000737:chemistry* / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry* / Q000494:pharmacology*; D003460:Crystallization; D018360:Crystallography, X-Ray; D003850:Deoxyribonuclease I / Q000378:metabolism; D007700:Kinetics; D008387:Marine Toxins / Q000737:chemistry / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000378:metabolism; D011817:Rabbits; D013844:Thiazoles / Q000737:chemistry* / Q000494:pharmacology*; D053778:Thiazolidines; D013947:Thymosin / Q000378:metabolism* / Q000494:pharmacology; D000099201:Thymosin beta(4)
chemical_list: D000199:Actins; D000255:Adenosine Triphosphate; D019086:Bridged Bicyclo Compounds, Heterocyclic; D003850:Deoxyribonuclease I; D008387:Marine Toxins; D013844:Thiazoles; D053778:Thiazolidines; D013947:Thymosin; D000099201:Thymosin beta(4); C037067:latrunculin A