Kurihara K, Hosoi K, Kodama A, Ueha T
Department of Oral Physiology, Meikai University, School of Dentistry, Saitama, Japan.
Biochim Biophys Acta. 1990 Jun 19;1039(2):234-40. doi: 10.1016/0167-4838(90)90191-h.
The alpha catalytic subunits of Na+/K(+)-ATPase were isolated from the kidney and brain of rats (alpha 1 and alpha 2, respectively). The antisera raised against these subunits were used as probes to analyze the isoform of catalytic subunits of Na+/K(+)-ATPase in various tissues of rats. Of 27 rat tissues examined, most had a catalytic subunit identical to alpha 1 but some, such as the nervous and muscle tissues, had both alpha 1 and alpha 2 isoforms as judged by their reactivities to antisera and their electrophoretic mobility. We found that the submandibular gland contained a new electrophoretic variant of immunoreactive alpha subunit (designated alpha(S) in this report) in addition to alpha 1 identical to those found in kidney and brain. The new variant, alpha(S), strongly cross-reacted with anti-alpha 1 antiserum, but to a lesser extent with anti-alpha 2 antiserum. The alpha(S) had a molecular mass which was found to be slightly less (approx. 90 kDa) than brain and kidney alpha 1. We examined whether or not the alpha(S) is formed by proteolytic cleavage of alpha subunits during preparation and concluded that this is not the case. The alpha(S) reacted with [gamma-32P]ATP, resulting in the formation of radioactive alpha subunit which was stabilized by 2 mM ouabain but which was labile in the presence of 70 mM potassium chloride. Since N-terminal amino acid sequence of alpha(S) protein [G()DKY()PAAVS] corresponds exactly and uniquely with the sequence of the alpha 1 chain between residues 1 and 11, it is very probable that alpha(S) protein originated from alpha 1 protein following the post-translational processing.
从大鼠的肾脏和大脑中分别分离出Na⁺/K⁺-ATP酶的α催化亚基（分别为α1和α2）。用针对这些亚基产生的抗血清作为探针，分析大鼠各种组织中Na⁺/K⁺-ATP酶催化亚基的同工型。在所检测的27种大鼠组织中，大多数组织具有与α1相同的催化亚基，但有些组织，如神经组织和肌肉组织，根据它们与抗血清的反应性及其电泳迁移率判断，同时具有α1和α2同工型。我们发现，下颌下腺除了含有与肾脏和大脑中发现的α1相同的亚基外，还含有一种新的免疫反应性α亚基的电泳变体（本报告中命名为α(S)）。这种新变体α(S)与抗α1抗血清强烈交叉反应，但与抗α2抗血清的交叉反应程度较小。α(S)的分子量略小于大脑和肾脏中的α1（约90 kDa）。我们检查了α(S)是否在制备过程中由α亚基的蛋白水解切割形成，并得出结论并非如此。α(S)与[γ-³²P]ATP反应，形成放射性α亚基，该亚基在2 mM哇巴因存在下稳定，但在70 mM氯化钾存在下不稳定。由于α(S)蛋白的N端氨基酸序列[G()DKY()PAAVS]与α1链第1至11位残基的序列完全且唯一对应，因此α(S)蛋白很可能是在翻译后加工后由α1蛋白产生的。
