Ray C, McKerrow J H
UCSF School of Medicine, Department of Pathology.
Mol Biochem Parasitol. 1992 Apr;51(2):239-49. doi: 10.1016/0166-6851(92)90074-t.
A Caenorhabditis elegans cysteine protease gene fragment, amplified by PCR using conserved eukaryotic protease gene sequences as primers, was used as a probe to isolate cDNA and genomic clones. The genomic clone, which had a coding sequence of 987 bp interrupted by 2 small introns, was physically mapped to the middle of linkage group V. The predicted amino acid sequence of the mature C. elegans cysteine protease was homologous to those of other eukaryotic cysteine proteases, particularly to that of the nematode parasite Haemonchus contortus (50%) and to the cathepsin B-like hemoglobinase of the trematode parasite Schistosoma mansoni (54%). The pro region of the C. elegans protease was homologous only to that of the H. contortus enzyme, implying a similar mechanism of protease activation. The C. elegans cysteine protease gene was temporally regulated: abundant 1.1-kb transcripts were detected in larvae and adults, but not in embryos. Transcription also was spatially regulated, occurring only in the intestine. Like the vitellogenin genes, which also are transcribed exclusively in the intestine, the 5' end of the C. elegans cysteine protease gene had at least one copy of each of 2 heptameric sequences which may be transcriptional regulatory elements governing gut-specific expression.
利用保守的真核生物蛋白酶基因序列作为引物，通过聚合酶链反应（PCR）扩增出秀丽隐杆线虫半胱氨酸蛋白酶基因片段，并将其用作探针来分离cDNA和基因组克隆。该基因组克隆的编码序列为987 bp，被2个小内含子打断，物理定位到连锁群V的中部。预测的秀丽隐杆线虫成熟半胱氨酸蛋白酶的氨基酸序列与其他真核生物半胱氨酸蛋白酶的序列同源，特别是与线虫寄生虫捻转血矛线虫的序列同源性为50%，与吸虫寄生虫曼氏血吸虫的组织蛋白酶B样血红蛋白酶的序列同源性为54%。秀丽隐杆线虫蛋白酶的前区仅与捻转血矛线虫酶的前区同源，这意味着蛋白酶激活机制相似。秀丽隐杆线虫半胱氨酸蛋白酶基因受时间调控：在幼虫和成虫中检测到丰富的1.1 kb转录本，但在胚胎中未检测到。转录也受空间调控，仅在肠道中发生。与同样仅在肠道中转录的卵黄蛋白原基因一样，秀丽隐杆线虫半胱氨酸蛋白酶基因的5'端至少有2个七聚体序列的各一个拷贝，这些序列可能是控制肠道特异性表达的转录调控元件。
