title: Behavior of N-phenylmaleimide-reacted muscle fibers in magnesium-free rigor solution.
abstract: Using x-ray diffraction and mechanical stiffness, the response of N-phenylmaleimide (NPM)-reacted cross-bridges to solutions containing different amounts of ATP and Mg2+ has been studied. In relaxing solution containing greater than millimolar amounts of ATP and Mg2+, NPM-treated muscle fibers give x-ray diffraction patterns and stiffness records, which are nearly indistinguishable from those of untreated relaxed fibers. In a solution devoid of added ATP, but with Mg2+ (rigor(+Mg) solution), the muscle fibers still give x-ray diffraction patterns and mechanical responses characteristic of relaxed muscle. The new finding reported here is that in a solution devoid of both ATP and Mg2+ (rigor(-Mg) solution containing EDTA with no added ATP), NPM-reacted cross-bridges do give rigor-like behavior. This is the first report that NPM-reacted cross-bridges, at least in the presence of EDTA, are capable of going into a strongly binding conformation.
authors.affiliation: Laboratory of Physical Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: S
authors.initials: S
authors.lastname: Xu
authors.forename: L C
authors.initials: LC
authors.lastname: Yu
authors.forename: M
authors.initials: M
authors.lastname: Schoenberg
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology*; D008301:Maleimides / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D011817:Rabbits; D012996:Solutions; D013997:Time Factors; D014961:X-Ray Diffraction
chemical_list: D008301:Maleimides; D012996:Solutions; D000255:Adenosine Triphosphate; C028525:N-phenylmaleimide; D008274:Magnesium