Pancer Z, Skorokhod A, Blumbach B, Müller W E
Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universität, Mainz, Germany.
Gene. 1998 Jan 30;207(2):227-33. doi: 10.1016/s0378-1119(97)00631-8.
The receptor tyrosine kinase of the marine sponge Geodia cydonium features two extracellular Ig-like domains in which we recently documented RT-PCR polymorphism among individuals. Genomic-PCR analysis presented here revealed 14 unique sequences from four sponges, differing predominantly in the sequence of an intron which splits the Ig-like domains. Nevertheless, analysis of putative coding regions in 19 distinct clones (156-159 aa) from seven sponges revealed 69 positions of nucleotide substitutions, 67.6% of them non-synonymous, translating into 43 positions of divergent residues. Excluding aa deletions, these 19 sequences share pairwise aa identities of 89-99%. In three sponges, four or five unique Ig-like coding regions were scored. PCR amplification across this intron revealed multiple bands, polymorphic among five of six sponges. Further substantiated by Southern and Northern blots, it is evident that the genome of G. cydonium harbors multicopies of moderately divergent Ig-like domains. Presently, this only appears paralleled by the human KIR multigene family of NK cells MHC class I-specific receptors, which consist of two or three moderately divergent extracellular Ig-like domains.
海洋海绵Geodia cydonium的受体酪氨酸激酶具有两个细胞外免疫球蛋白样结构域，我们最近记录了个体间的RT-PCR多态性。本文展示的基因组PCR分析从四个海绵中揭示了14个独特序列，主要差异在于一个内含子的序列，该内含子将免疫球蛋白样结构域分开。然而，对来自七个海绵的19个不同克隆（156 - 159个氨基酸）的推定编码区分析显示，有69个核苷酸替换位置，其中67.6%为非同义替换，转化为43个不同残基位置。排除氨基酸缺失，这19个序列的两两氨基酸同一性为89 - 99%。在三个海绵中，记录到四个或五个独特的免疫球蛋白样编码区。跨越该内含子的PCR扩增显示多条带，在六个海绵中的五个中具有多态性。经Southern和Northern印迹进一步证实，显然Geodia cydonium的基因组含有多个中度不同的免疫球蛋白样结构域的拷贝。目前，这仅与人类NK细胞MHC I类特异性受体的KIR多基因家族相似，该家族由两个或三个中度不同的细胞外免疫球蛋白样结构域组成。
