Detail of "139609-20-4"

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Conformational changes in the foot protein of the sarcoplasmic reticulum assessed by site-directed fluorescent labeling

Conformational changes in the foot protein of the sarcoplasmic reticulum assessed by site-directed fluorescent labeling. Kang, J. J.; Tarcsafalvi, A.; Carlos, A. D.; Fujimoto, E.; Shahrokh, Z.; Thevenin, B.Chemicals with cas numbers 15662-33-6 and 139609-20-4 also play role. J. M.; Shohet, S. B.; Ikemoto, N. (Dep. Muscle Res., Boston Biomed. Res. Inst., Boston, MA 02114, USA). Biochemistry, 31(12), 3288-93 (English) 1992. CODEN: BICHAW. ISSN: 0006-2960. DOCUMENT TYPE: Journal CA Section: 9 (Biochemical Methods) Section cross-reference(s): 6 Ca2+ release from sarcoplasmic reticulum during excitation-contraction coupling is likely to be mediated by conformational changes in the foot protein moiety of the triadic vesicles. As a preparative step toward the studies of dynamic conformational changes in the foot protein moiety, a new method was developed that permits specific labeling of the foot protein moiety of the isolated membranes with a fluorophore. A novel fluorescent cleavable photoaffinity crosslinking reagent, sulfosuccinimidyl 3-((2-(7-azido-4-methylcoumarin-3-acetamido)ethyl)dithio)propionate (SAED), was conjugated with site-directed carriers, polylysine (Ca2+-release inducer) and neomycin (Ca2+-release blocker). The conjugates were allowed to bind to polylysine- and neomycin-binding sites of the heavy fraction of SR (HSR). After photolysis, the crosslinking reagent was cleaved by redn. and the fluorescently labeled HSR was sepd. from the carriers by centrifugation. These procedures led to specific incorporation of the methylcoumarin acetate (MCA) into the foot protein. Polylysine and neomycin bound to different sites of the foot protein, since neomycin, at release-blocking concns., did not interfere with polylysine binding. The fluorescence intensity of the foot protein labeled with the carrier, neomycin, showed biphasic changes as a function of ryanodine concn. (increasing up to 1 mM ryanodine and decreasing about it), while with the carrier polylysine, ryanodine induced no change in fluorescence intensity. In contrast, the fluorescence intensity of the foot protein labeled with each of the two carriers, neomycin and polylysine, showed almost identical calcium dependence (first increasing from 0.1 mM to about 3.0 mM calcium concn., and then decreasing at higher calcium concns.). These results suggest that modulation of Ca2+ release by ryanodine involves a local conformational change not only in the neomycin-binding region but also in the polylysine-binding region. .