Caroni P, Rothenfluh A, McGlynn E, Schneider C
Friedrich Miescher Institute, Basel, Switzerland.
J Biol Chem. 1991 Jun 15;266(17):10739-42.
Cyclophilin is an abundant and ubiquitous cytosolic protein that is conserved throughout evolution from man to bacteria. It is the target of the immunosuppressive drug cyclosporin A. Cyclophilin has peptidyl-prolyl cis/trans-isomerase activity, and it accelerates protein folding in vitro, suggesting that it might be involved in the folding of cytosolic proteins. We describe a novel cyclophilin-like protein, S-cyclophilin, in the chick. Analysis of S-cyclophilin cDNA revealed the presence of a signal sequence followed by an open reading frame coding for a protein very similar to cytosolic cyclophilin, except for the presence of unique additional short amino acid segments at the N and C termini of the protein. S-Cyclophilin mRNA was abundant and present in all embryonic chick tissues tested. Cyclophilin and S-cyclophilin are coded by separate genes in the chick genome. Recombinant S-cyclophilin was expressed in insect cells by means of the baculovirus system. Pulse-chase experiments revealed that a significant fraction of newly synthesized recombinant S-cyclophilin was rapidly secreted into the culture medium. Our findings indicate that cyclophilins are associated with most if not all intra- and extracellular compartments and suggest that enzyme-assisted conformational conversions in proteins might also take place in post-endoplasmic reticulum compartments, possibly including the extracellular space.
亲环蛋白是一种丰富且普遍存在的胞质蛋白，从人类到细菌在整个进化过程中都保守存在。它是免疫抑制药物环孢素A的作用靶点。亲环蛋白具有肽基脯氨酰顺反异构酶活性，并且在体外能加速蛋白质折叠，这表明它可能参与胞质蛋白的折叠。我们在鸡中描述了一种新型亲环蛋白样蛋白，即S-亲环蛋白。对S-亲环蛋白cDNA的分析显示，其存在一个信号序列，随后是一个开放阅读框，编码一种与胞质亲环蛋白非常相似的蛋白质，只是在该蛋白质的N端和C端存在独特的额外短氨基酸片段。S-亲环蛋白mRNA在所有测试的鸡胚胎组织中都丰富存在。亲环蛋白和S-亲环蛋白在鸡基因组中由不同基因编码。重组S-亲环蛋白通过杆状病毒系统在昆虫细胞中表达。脉冲追踪实验表明，新合成的重组S-亲环蛋白有很大一部分迅速分泌到培养基中。我们的研究结果表明，亲环蛋白与大多数（如果不是全部）细胞内和细胞外区室相关，并表明蛋白质中的酶辅助构象转换也可能在内质网后区室中发生，可能包括细胞外空间。
