Pang D C, Briggs F N
J Biol Chem. 1977 May 25;252(10):3262-6.
Isolated sarcotubular membranes (SR) from skeletal muscle bound 3.7 nmol of beta, gamma-methylene [8-3H]ATP (AMP-PCP) per mg of membrane protein. Only one class of binding site was identified and the dissociation constant (K) for this site was 1.5 X 10(-5) M. Addition of 0.05% Triton X-100 increased the number of binding sites to 5.7 nmol/mg. ATP and ADP competitively inhibited AMP-PCP binding. The dissociation constants for ATP and ADP were 3.5 X 10(-5) M and 3.3 X 10(-6) M, respectively. Since this data was obtained in the presence of 5 mM EDTA, it was established that the sarcoplasmic reticulum has a high affinity for the metal free forms of ATP, ADP, and AMP-PCP. Magnesium concentrations in excess of 1 X 10(-4) M inhibited AMP-PCP binding. Lower concentrations of magnesium had little effect on AMP-PCP binding. The effect of calcium on AMP-PCP binding was biphasic. Calcium concentration between 1 X 10(-6) and 1 X 10(-4) M inhibited AMP-PCP binding. Inhibition was maximal at 1 X 10(-5) M. Calcium concentration above 1 X 10(-4) M facilitated analogue binding. Possible sites of magnesium and calcium actions are discussed.
从骨骼肌分离得到的肌质网膜（SR）每毫克膜蛋白结合3.7纳摩尔的β，γ-亚甲基[8-³H]ATP（AMP-PCP）。仅鉴定出一类结合位点，该位点的解离常数（K）为1.5×10⁻⁵M。添加0.05%的 Triton X-100可使结合位点数量增加至5.7纳摩尔/毫克。ATP和ADP竞争性抑制AMP-PCP的结合。ATP和ADP的解离常数分别为3.5×10⁻⁵M和3.3×10⁻⁶M。由于该数据是在5 mM EDTA存在的情况下获得的，因此确定肌质网对无金属形式的ATP、ADP和AMP-PCP具有高亲和力。超过1×10⁻⁴M的镁浓度会抑制AMP-PCP的结合。较低浓度的镁对AMP-PCP的结合影响不大。钙对AMP-PCP结合的影响是双相的。钙浓度在1×10⁻⁶至1×10⁻⁴M之间会抑制AMP-PCP的结合。在1×10⁻⁵M时抑制作用最大。高于1×10⁻⁴M的钙浓度会促进类似物的结合。讨论了镁和钙作用的可能位点。
