Lachumanan R, Armugam A, Tan C H, Jeyaseelan K
Department of Biochemistry, Faculty of Medicine, National University of Singapore, Singapore.
FEBS Lett. 1998 Aug 14;433(1-2):119-24. doi: 10.1016/s0014-5793(98)00894-1.
We report the genomic structure, organization and the presence of multiple isoforms of the gene encoding cardiotoxins (CTX) of Naja naja sputatrix. The cardiotoxin gene consists of six CTX isoforms, each (2.2 kb) having three exons and two introns. Two possible transcription initiation sites as well as consensus TATA boxes and transcription factor binding motifs, AP-2, NFIL-6/C/EBP, NF-kappaB and PuF have been identified in the 5'-region of the gene. The CTX gene isoforms show nucleotide variations at specific segments in exon 2 and exon 3, which correspond to the functional domains in the three-finger loop structure of the cardiotoxin molecule. The diverse functions of cardiotoxins together with our findings suggest that the cardiotoxin gene isoforms may have evolved under adaptive pressure through a positive Darwinian selection process.
我们报道了眼镜蛇（Naja naja sputatrix）心脏毒素（CTX）编码基因的基因组结构、组织形式以及多种异构体的存在情况。心脏毒素基因由六种CTX异构体组成，每种异构体（2.2 kb）包含三个外显子和两个内含子。在该基因的5'区域已鉴定出两个可能的转录起始位点以及共有TATA盒和转录因子结合基序，即AP-2、NFIL-6/C/EBP、NF-κB和PuF。CTX基因异构体在第2外显子和第3外显子的特定区段显示出核苷酸变异，这些区段对应于心脏毒素分子三指环结构中的功能域。心脏毒素的多种功能以及我们的研究结果表明，心脏毒素基因异构体可能是在适应性压力下通过积极的达尔文选择过程进化而来的。
