Verchot J, Koonin E V, Carrington J C
Department of Biology, Texas A&M University, College Station 77843.
Virology. 1991 Dec;185(2):527-35. doi: 10.1016/0042-6822(91)90522-d.
The polyprotein encoded by plant potyviruses is proteolytically processed to at least eight mature products by viral-encoded proteinases. While the proteinases that catalyze processing at most of the cleavage sites have been identified, the enzyme responsible for cleavage between the 35-kDa protein and helper component-proteinase (HC-Pro), near the N-terminus of the viral polyprotein, has not been mapped or characterized previously. Polyproteins containing the 35-kDa protein and HC-Pro were synthesized in the wheat germ system using defined RNA transcripts and were demonstrated to undergo proteolysis to generate products that resemble fully processed proteins. The C-terminal half of the 35-kDa protein was found to be required for proteolysis, whereas most of the HC-Pro sequence was dispensable. Amino acid substitutions affecting three positions, each of which are conserved in the 35-kDa protein encoded by five potyviruses, were shown to inhibit protein processing. These data suggest that the 35-kDa protein functions as a proteinase to cleave at its C-terminus. A model that accounts for all proteolytic processing events in the potyviral polyprotein is presented.
植物马铃薯Y病毒编码的多聚蛋白通过病毒编码的蛋白酶被蛋白水解加工成至少8种成熟产物。虽然催化大多数切割位点加工的蛋白酶已被鉴定出来，但负责在病毒多聚蛋白N端附近的35 kDa蛋白和辅助成分蛋白酶（HC-Pro）之间切割的酶此前尚未定位或表征。使用特定的RNA转录本在小麦胚系统中合成了包含35 kDa蛋白和HC-Pro的多聚蛋白，并证明其会发生蛋白水解以产生类似于完全加工蛋白的产物。发现35 kDa蛋白的C端一半对于蛋白水解是必需的，而大部分HC-Pro序列是可有可无的。影响三个位置的氨基酸取代（这三个位置在五种马铃薯Y病毒编码的35 kDa蛋白中均保守）被证明会抑制蛋白加工。这些数据表明35 kDa蛋白作为一种蛋白酶在其C端进行切割。本文提出了一个解释马铃薯Y病毒多聚蛋白中所有蛋白水解加工事件的模型。
