Slow transition of phosphoenzyme from ADP-sensitive to ADP-insensitive forms in solubilized Ca2+, Mg2+-ATPase of sarcoplasmic reticulum: evidence for retarded dissociation of Ca2+ from the phosphoenzyme. |
| |
Authors: | Y Takakuwa T Kanazawa |
| |
Affiliation: | Department of Biochemistry Asahikawa Medical College Asahikawa 078-11, Japan |
| |
Abstract: | Solubilized Ca2+, Mg2+-ATPase of sarcoplasmic reticulum was phosphorylated with ATP without added MgCl2. The phosphoenzyme formed was ADP-sensitive. Ca2+ in the medium was chelated after phosphorylation. This induced a slow transition of the phosphoenzyme from ADP-sensitive to ADP-insensitive forms. The ADP-sensitivity was restored by subsequent addition of CaCl2. These results showed that the transition was caused by dissociation of Ca2+ bound to the phosphoenzyme. Further observations indicated that, when Ca2+ in the medium was chelated, Ca2+ bound to the phosphoenzyme was dissociated much more slowly than Ca2+ bound to the dephosphoenzyme. This suggests a possible formation of the occluded form of the Ca2+-binding site in the phosphoenzyme. |
| |
Keywords: | EGTA ethylene glycol bis(β-aminoethyl ether)-N,N′-tetraacetic acid |
本文献已被 ScienceDirect 等数据库收录! |