Shoemaker C B, Ramachandran H, Landa A, dos Reis M G, Stein L D
Department of Tropical Public Health, Harvard School of Public Health, Boston, MA 02115.
Mol Biochem Parasitol. 1992 Jul;53(1-2):17-32. doi: 10.1016/0166-6851(92)90003-3.
The complete coding DNA for a Schistosoma mansoni homologue of the epidermal growth factor receptor (SER) was characterized from cDNA clones obtained by homology to the tyrosine kinase domain of erbB. The DNA sequence predicts a 200-kDa translation product that contains a secretory leader, a cysteine-rich extracellular domain, a hydrophobic transmembrane sequence, and an intracellular tyrosine kinase domain. The SER transcript is present in cercariae and adult schistosomes. In addition to SER transcripts, schistosomes produce at least 3 variant transcripts encoding truncated SER products that include the secretory leader and a small portion of the extracellular domain followed by short sequences of unrelated, C-terminal amino acids. Based on these sequences, 2 of the variant mRNAs (class 2 and 5) appear to encode soluble, secreted proteins while one (class 4) encodes an SER variant protein with a hydrophobic C-terminus that may serve as a membrane anchor. Class 2 SER variant transcripts are present at levels comparable to SER transcripts in adult worms but are not detected in cercariae. Class 4 and 5 SER variant transcripts are also found within adult worms but at lower levels. Genomic cloning and characterization demonstrate that the variant SER transcripts arise through alternative splicing of the SER gene.
通过与erbB酪氨酸激酶结构域的同源性从cDNA克隆中鉴定出曼氏血吸虫表皮生长因子受体（SER）的完整编码DNA。该DNA序列预测了一个200 kDa的翻译产物，其包含一个分泌前导序列、一个富含半胱氨酸的细胞外结构域、一个疏水跨膜序列和一个细胞内酪氨酸激酶结构域。SER转录本存在于尾蚴和成虫血吸虫中。除了SER转录本外，血吸虫还产生至少3种编码截短SER产物的可变转录本，这些产物包括分泌前导序列和细胞外结构域的一小部分，后面跟着不相关的C端氨基酸短序列。基于这些序列，其中2种可变mRNA（2类和5类）似乎编码可溶性分泌蛋白，而另一种（4类）编码具有疏水C端的SER变体蛋白，该C端可能作为膜锚定物。2类SER可变转录本在成虫中的水平与SER转录本相当，但在尾蚴中未检测到。4类和5类SER可变转录本也在成虫中发现，但水平较低。基因组克隆和鉴定表明，可变SER转录本是通过SER基因的可变剪接产生的。
