King D P, Schrenzel M D, McKnight M L, Reidarson T H, Hanni K D, Stott J L, Ferrick D A
International Program for Marine Mammal Health, The Marine Mammal Center, Marin Headlands, GGNRA, Sausalito, CA 94965.
Immunogenetics. 1996;43(4):190-5. doi: 10.1007/BF00587299.
Using polymerase chain reaction, interleukin-6 (IL-6) cDNA fragments from harbor seal (Phoca vitulina), killer whale (Orcinus orca), and Southern sea otter (Enhydra lutris nereis) were cloned and sequenced. For all three species, a continuous open reading frame encoding 203 residues for harbor seal, 199 residues for killer whale, and 201 residues for sea otter with stop codons located at analogous positions were identified. These fragments correspond to nucleotides 71 - 753 of the human IL-6 transcript and represent 96% of the complete coding nucleotides. Comparison of these marine mammal sequences with other published mammalian IL-6 cDNA demonstrated that both harbor seal and sea otter IL-6 had most similarity to that of other terrestrial carnivores (Mustelidae and Canidae), while killer whale had highest identity with ruminants (Bovidae and Ovidae). Among the three marine mammal species characterized, as well as cDNA sequences from nine other species, 40 invariant amino acids, including a number of residues situated at the putative gp80 and gp130 receptor binding sites, were identified. The presence of invariant amino acids within the receptor-binding portion of IL-6 for twelve different species suggests these positions are essential for biological activity of IL-6 and, moreover, likely account for the cross-reactivity among different mammalian IL-6-like activities in mouse bioassays. An additional significant finding was the presence of several variant residues only within the mouse putative IL-6 receptor binding region, which may account for observations of restricted cross-reactivity of mouse IL-6-like activity in human bioassays. Together, these findings provide insights into the evolution of the mammalian IL-6 gene and additional valuable information regarding amino acid residues essential for the biological activity of mammalian IL-6.
利用聚合酶链反应，对斑海豹（Phoca vitulina）、虎鲸（Orcinus orca）和南海獭（Enhydra lutris nereis）的白细胞介素-6（IL-6）cDNA片段进行了克隆和测序。对于这三个物种，均鉴定出一个连续的开放阅读框，该阅读框编码斑海豹203个残基、虎鲸199个残基、海獭201个残基，且终止密码子位于类似位置。这些片段对应于人类IL-6转录本的核苷酸71 - 753，占完整编码核苷酸的96%。将这些海洋哺乳动物序列与其他已发表的哺乳动物IL-6 cDNA进行比较，结果表明斑海豹和海獭的IL-6与其他陆生食肉动物（鼬科和犬科）的IL-6最为相似，而虎鲸的IL-6与反刍动物（牛科和羊科）的IL-6具有最高的同一性。在所表征的三种海洋哺乳动物物种以及其他九个物种的cDNA序列中，鉴定出40个不变氨基酸，其中包括一些位于假定的gp80和gp130受体结合位点的残基。IL-6受体结合部分在12个不同物种中存在不变氨基酸，这表明这些位置对于IL-6的生物学活性至关重要，此外，这可能是小鼠生物测定中不同哺乳动物IL-6样活性之间交叉反应的原因。另一个重要发现是，仅在小鼠假定的IL-6受体结合区域内存在几个可变残基，这可能解释了在人类生物测定中小鼠IL-6样活性交叉反应受限的现象。总之，这些发现为哺乳动物IL-6基因的进化提供了见解，并提供了有关哺乳动物IL-6生物学活性所必需的氨基酸残基的其他有价值信息。
