Plewe G, Jahn R, Immelmann A, Bode C, Söling H D
FEBS Lett. 1984 Jan 23;166(1):96-103. doi: 10.1016/0014-5793(84)80052-6.
Stimulation of secretion in exocrine cells by agonists involving cAMP as second messenger is associated with the phosphorylation of a specific membrane-associated 22.4-kDa protein (protein III) (Jahn et al.). Here it is shown by subcellular fractionation of rat parotid gland lobules that protein III is associated with the endoplasmic reticulum. The submicrosomal fractions containing protein III, also contain the ATP-dependent microsomal calcium pump activity. Protein III in microsomal subfractions can be phosphorylated in vitro with catalytic subunit from cAMP-dependent protein kinase. Phosphorylated protein III contains exclusively P-serine. Protein III can be removed from ER-membranes with acid chloroform-methanol or Triton X-114, but not by high salt wash indicating that it is tightly associated with the membranes. Protein III is smaller than phospholamban and, in contrast to phospholamban, resistant to heating in SDS. A relationship between phosphorylation of protein III and microsomal calcium sequestration is discussed.
以环磷酸腺苷（cAMP）作为第二信使的激动剂刺激外分泌细胞分泌，与一种特定的膜相关22.4 kDa蛋白（蛋白III）的磷酸化有关（扬恩等人）。本文通过对大鼠腮腺小叶进行亚细胞分级分离表明，蛋白III与内质网相关。含有蛋白III的亚微粒体部分，也含有ATP依赖的微粒体钙泵活性。微粒体亚组分中的蛋白III在体外能用依赖cAMP的蛋白激酶的催化亚基进行磷酸化。磷酸化的蛋白III仅含磷酸丝氨酸。蛋白III可用酸性氯仿 - 甲醇或曲拉通X - 114从内质网膜上去除，但不能通过高盐洗涤去除，这表明它与膜紧密结合。蛋白III比受磷蛋白小，并且与受磷蛋白不同，在SDS中耐热。文中讨论了蛋白III的磷酸化与微粒体钙螯合之间的关系。
