Different behavior of protein B23/nucleophosmin and UBF in HeLa cells during apoptosis

The behavior of UBF (upstream binding factor) and nucleophosmin in HeLa and HeLa-Bcl-2 cells during apoptosis induced by TNF-α, emetine, and their mixture was investigated. A pronounced apoptosis was achieved only in HeLa cells treated with a mixture of the inducers. Immunoblotting analysis of UBF and nucleophosmin in samples containing different portions of cells with apoptotic nuclei was carried out. It showed that UBF was proteolytically cleaved giving a stable 76-kDa fragment. Increasing content of the fragment during apoptosis correlated with the level of cells containing apoptotic nuclei and with a decrease in the content of full-sized UBF. Determination of N- and C-terminal sequences of UBF and 76-kDa fragment allowed us not only to characterize UBF at the protein level, but also to describe the site of the apoptosis-specific proteolysis. Nucleophosmin did not undergo proteolytic cleavage during apoptosis and its content was unchanged even in a sample containing 100% of cells with apoptotic nuclei. However in cells reached terminal stages of apoptosis, the balance between mono- and oligomeric forms of nucleophosmin changed due to depletion of monomeric forms and appearance of two additional oligomeric forms with lower molecular weight.

钻井液用页岩抑制剂研究进展

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酶的寡聚结构与催化稳定性

酶的结构与催化稳定性是生物催化与转化过程中的研究热点之一。与单体酶相比,寡聚酶在进化过程中亚基之间的聚合使其在结构和功能上具有一定的优越性,然而寡聚酶独特的四级结构导致其在制备和应用中存在诸多问题,如制备效率低、催化位点利用率低、催化稳定性差等,其中亚基解离导致的催化稳定性问题在很大程度上限制了其工业化应用。目前,介质工程、多亚基固定化、亚基界面工程和融合蛋白策略被应用于寡聚酶的催化稳定性改造,而寡聚酶至单体酶的改造策略则试图从根本上解决寡聚酶的制备和应用问题,具有较好的应用前景。本文介绍了酶的寡聚结构演替所产生的新功能,总结了寡聚酶在制备和应用中存在的问题,重点阐述了提高寡聚酶制备效率和催化稳定性的策略。