Studies on the small nuclear ribonucleoprotein particles that act as autoantigens in rheumatic disease
Studies on the small nuclear ribonucleoprotein particles that act as autoantigens in rheumatic disease
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在风湿性疾病中充当自身抗原的小核核糖核蛋白颗粒的研究
DOI：
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发表时间：
1982
期刊：
影响因子：
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通讯作者：
A. Macgillivray
中科院分区：
文献类型：
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作者：
M. Sadaie;T. Jing;A. Macgillivray
KCl制备的膜的潜伏大鼠酶的初始失活相为一级（k_i = 0.07-0.08 min ~（-1）），当假定埋藏酶与暴露酶的比率为（IBI/[Al]）为15（即94%的酶分子被掩埋），一级速率常数k1和k2分别为0.002min-1和0.018min-1。对于蔗糖制备的微粒体膜，在存在去污剂的情况下测定的k值低于KCl制备的级分的k值，并且可以合理地假设，在不存在Triton的情况下，蔗糖制备的膜的k值也会更低。如果单独的k1从0.08min-1降低到0.028min-1，则该模型现在预测双相反应;初始失活如此缓慢，以至于被第二激活相所掩盖。得到与实验曲线非常相似的结果，如果。此外，IBlo/IAlo从15增加到50（代表掩埋酶的比例增加到98%）。对于类似的。但蔗糖制备组分的豚鼠转移酶的响应不太显著。当k = 0.014min ~（-1）和lB~（-0）/lA ~（-0）= 20时，模型与实验数据有较好的拟合。这意味着大约95%的豚鼠酶分子被掩埋。为了模拟胰蛋白酶（Ki = 0.070.08min ~（-1））对KCl制备的膜的非潜伏性豚鼠酶的快速失活，需要将~Blo/ lAlo降低到小于I的值，这也与这些酶分子主要位于膜表面附近的证据相一致。这些结果为我们的观点提供了额外的支持，即转移酶对胰蛋白酶的不同反应是由于微粒体膜内酶分子位置的差异。提示酶的潜伏程度与酶分子占据深埋膜位点的比例有关。
latent rat enzyme of KCI-prepared membranes the initial inactivation phase was first order (k, = 0.07-0.08 min-I), and a triphasic curve similar to that observed was generated by the model when it was assumed that the ratio of buried to exposed enzyme (IBI,/[Al,) is I5 (i.e. 94% of the enzyme molecules are buried) and the first-order rate constants k , and k , are 0.002 min-' and 0.018 min-' respectively. With sucroseprepared microsomal membranes the value of k , determined in presence of detergent is lower than that for KCI-prepared fractions, and it is reasonable to assume that k , for sucroseprepared membranes in the absence of Triton also will be lower. If k , alone is decreased from 0.08min-' to 0.028min-I, the model now predicts a biphasic response; the initial inactivation is so slow that it is obscured by the second activation phase. A close resemblance to the experimental curve is obtained if. in addition, IBlo/IAIo is increased from 15 to 50 (representing an increase in the proportion of the buried enzyme to 98%). For the similar. but less marked, response of the guinea-pig transferase of sucrose-prepared fractions the model yields a reasonable fit to the experimental data when k , is 0.014min-' and lB~o/lAlo is 20. This implies that about 95% of the guinea-pig enzyme molecules are buried. To simulate the rapid inactivation by trypsin (k , = 0.070.08min-I) of the non-latent guinea-pig enzyme of KCIprepared membranes it is necessary to decrease ~Blo/ lAlo to values less than I , and this is also consistent with evidence suggesting that these enzyme molecules are located mainly near the membrane surface. These results provide additional support for our view that the different responses of transferases to trypsin are due to differences in the locations of enzyme molecules within microsomal membranes. and they suggest that the degree of enzyme latency is related to the proportion of enzyme molecules occupying deeply-buried membrane sites.