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首页> 外文期刊>Molecular and Cellular Biology >Molecular cloning and functional analysis of three subunits of yeast proteasome.
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Molecular cloning and functional analysis of three subunits of yeast proteasome.

机译：酵母蛋白酶体三个亚基的分子克隆和功能分析。

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The genes encoding three subunits of Saccharomyces cerevisiae proteasome were cloned and sequenced. The deduced amino acid sequences were homologous not only to each other (30 to 40% identity) but also to those of rat and Drosophila proteasomes (25 to 65% identity). However, none of these sequences showed any similarity to any other known sequences, including various proteases, suggesting that these proteasome subunits may constitute a unique gene family. Gene disruption analyses revealed that two of the three subunits (subunits Y7 and Y8) are essential for growth, indicating that the proteasome and its individual subunits play an indispensable role in fundamental biological processes. On the other hand, subunit Y13 is not essential; haploid cells with a disrupted Y13 gene can proliferate, although the doubling time is longer than that of cells with nondisrupted genes. In addition, biochemical analysis revealed that proteasome prepared from the Y13 disrupted cells contains tryptic and chymotryptic activities equivalent to those of nondisrupted cells, indicating that the Y13 subunit is not essential for tryptic or chymotryptic activity. However, the chymotryptic activity of the Y13 disrupted cells is not dependent on sodium dodecyl sulfate (SDS), an activator of proteasome, since nearly full activity was observed in the absence of SDS. Thus, the activity in proteasome of the Y13 disrupted cells might result in unregulated intracellular proteolysis, thus leading to the prolonged cell cycle. These results indicate that cloned proteasome subunits having similar sequences to the yeast Y13 subunit are structural, but not catalytic, components of proteasome. It is also suggested that two subunits (Y7 and Y8) might occupy positions essential to proteasome structure or activity, whereas subunit Y13 is in a nonessential but important position.
机译：克隆了酿酒酵母蛋白酶体三个亚基的编码基因并进行了测序。推导的氨基酸序列不仅彼此同源（30至40％同一性），而且与大鼠和果蝇蛋白酶体的同源（25至65％同一性）。然而，这些序列均未显示出与任何其他已知序列（包括各种蛋白酶）的任何相似性，表明这些蛋白酶体亚基可能构成独特的基因家族。基因破坏分析表明，三个亚基中的两个（亚基Y7和Y8）对于生长至关重要，这表明蛋白酶体及其单个亚基在基本生物学过程中起着不可或缺的作用。另一方面，亚基Y13不是必不可少的。 Y13基因被破坏的单倍体细胞可以增殖，尽管倍增时间要比未破坏基因的细胞长一倍。此外，生化分析表明，由Y13破坏的细胞制备的蛋白酶体具有与未破坏的细胞相同的胰蛋白酶和胰凝乳蛋白酶活性，表明Y13亚基对于胰蛋白酶或胰凝乳蛋白酶活性不是必需的。但是，Y13破坏细胞的胰凝乳蛋白酶活性不依赖于十二烷基硫酸钠（SDS）（一种蛋白酶体的活化剂），因为在不存在SDS的情况下观察到几乎全部活性。因此，Y13破坏的细胞在蛋白酶体中的活性可能导致细胞内蛋白水解失控，从而导致细胞周期延长。这些结果表明，具有与酵母Y13亚基相似序列的克隆的蛋白酶体亚基是蛋白酶体的结构性而非催化性组分。还建议两个亚基（Y7和Y8）可能占据蛋白酶体结构或活性必不可少的位置，而亚基Y13处于不必要但重要的位置。

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