Böhme R, Bumann J, Aeckerle S, Malchow D
Fakultät für Biologie, Universität Konstanz, F.R.G.
Biochim Biophys Acta. 1987 Nov 2;904(1):125-30. doi: 10.1016/0005-2736(87)90093-9.
Chemotactic stimulation of Dictyostelium discoideum induces an uptake of Ca2+ by the cells followed by a release of Ca2+. In this study we investigated the mechanism of Ca2+ release and found that it was inhibited by La3+, Cd2+ and azide. Ca2+ release occurred in the absence of external Na+, indicating that an Na+/Ca2+ exchange was not involved. Plasma membranes contained high- and low-affinity ATPase activities. Apparent K0.5 values were 8 microM for the major Mg2+-ATPase and 1.1 microM for the high-affinity Ca2+-ATPase, respectively. The Mg2+-ATPase activity was inhibited by elevated concentrations of Ca2+, whereas both Ca2+-ATPases were active in the absence of added Mg2+. The activities of the Ca2+-ATPases were not modified by calmodulin. The high-affinity Ca2+-ATPase was competitively inhibited by La3+ and Cd2+; we suggest that this high-affinity enzyme mediates the release of Ca2+ from D. discoideum cells.
对盘基网柄菌的趋化性刺激会诱导细胞摄取Ca2+，随后释放Ca2+。在本研究中，我们研究了Ca2+释放的机制，发现它受到La3+、Cd2+和叠氮化物的抑制。Ca2+释放在没有外部Na+的情况下发生，表明不涉及Na+/Ca2+交换。质膜含有高亲和力和低亲和力的ATP酶活性。主要的Mg2+-ATP酶的表观K0.5值分别为8 microM，高亲和力Ca2+-ATP酶的表观K0.5值为1.1 microM。Mg2+-ATP酶活性受到Ca2+浓度升高的抑制，而两种Ca2+-ATP酶在没有添加Mg2+的情况下均有活性。Ca2+-ATP酶的活性不受钙调蛋白的影响。高亲和力Ca2+-ATP酶受到La3+和Cd2+的竞争性抑制；我们认为这种高亲和力酶介导了盘基网柄菌细胞中Ca2+的释放。
