Chan K M, Davies P L, Childs S, Veinot L, Ling V
Department of Biochemistry, Queen's University, Kingston, Canada.
Biochim Biophys Acta. 1992 Nov 15;1171(1):65-72. doi: 10.1016/0167-4781(92)90140-u.
In mammals, P-glycoprotein (P-gp) is encoded by two or more highly conserved genes that differ in their abilities to transport drugs. One isoform class (class I) is consistently associated with the multidrug resistance phenotype, while the other (class III) is not. This study was designed to enumerate the P-gp genes in fish and determine how they are related to the two functional classes already defined in mammals. Southern blot analysis using a conserved single exon from the 3' terminal region of hamster P-gp cDNA (pEX1-172) as a probe indicated that there were two P-gp genes in right-eye flounders. Subsequently, two sets of clones were isolated from a winter flounder genomic library that correspond to the 3' ends of the two flounder P-gp genes. Sequence analysis was done on two key areas: the 3' ATP binding site and the 3' terminal exon, both of which were found to be homologous with their mammalian counterparts. Despite high levels of sequence identity in the predicted coding regions of the gene fragments it has not been possible to use these sequences to relate the homologs to particular mammalian classes of P-gp genes, perhaps because of gene conversion between mammalian P-gp genes. These cloned sequences are the first set of P-gp genes reported in lower vertebrates and will be useful for delineating the expression of P-gp genes in fish and understanding the role of P-gp in fish physiology.
在哺乳动物中，P-糖蛋白（P-gp）由两个或更多高度保守的基因编码，这些基因在运输药物的能力上存在差异。一种同工型类别（I类）始终与多药耐药表型相关，而另一种（III类）则不然。本研究旨在列举鱼类中的P-gp基因，并确定它们与哺乳动物中已定义的两个功能类别之间的关系。使用仓鼠P-gp cDNA（pEX1-172）3'末端区域的保守单外显子作为探针进行的Southern印迹分析表明，右眼比目鱼中有两个P-gp基因。随后，从冬比目鱼基因组文库中分离出两组克隆，它们对应于两种比目鱼P-gp基因的3'末端。对两个关键区域进行了序列分析：3'ATP结合位点和3'末端外显子，发现它们与哺乳动物的对应区域同源。尽管基因片段的预测编码区域具有高度的序列同一性，但由于哺乳动物P-gp基因之间的基因转换，尚无法利用这些序列将同源物与特定的哺乳动物P-gp基因类别相关联。这些克隆序列是在低等脊椎动物中报道的第一组P-gp基因，将有助于描绘鱼类中P-gp基因的表达情况，并了解P-gp在鱼类生理学中的作用。
