Maruyama Tadashi, Suzuki Rintaro, Furutani Masahiro
Japan Marine Science and Technology Center, 2-15 Natsushima-cho, Yokosuka-shi, Kanagawa 237-0061, Japan.
Front Biosci. 2004 May 1;9:1680-720. doi: 10.2741/1361.
PPIases are ubiquitous in living organisms. While three families of PPIases, cyclophilin (CyP), FK506 binding protein (FKBP) and parvulin (Pvn), have been studied in detail in Eukarya and Bacteria (eubacteria), little is known about archaeal PPIases. Among 13 cyclophilins found in Archaea, only Halobacterium cyclophilin (HbsCyP19) has been characterized. This is a cyclosporin A (CsA) sensitive CyP with a molecular weight of 19.4 kDa. The PPIase activity and CsA sensitivity of HbsCyP19 is higher at higher salt concentration in the medium. No parvulin except a homolog in Cenarchaeum symbiosum has been found in Archaea. Two types of FKBPs, 26-30 kDa long-type and 17-18 kDa short-type FKBP, have been found in Archaea. Up to date, 12 short-type FKBPs and 18 long-type FKBPs have been known. The short-type FKBPs and N-terminal sequences of the long-type FKBPs are similar to each other and show homology to human FKBP12 (HsFKBP12). However, they have two insertion sequences in the regions corresponding to bulge and flap loops of HsFKBP12. The long-type archaeal FKBPs have additional ca. 100 amino-acid sequences at their C-terminal regions. A short-type archaeal FKBP from Methanothermococcus thermolithotrophicus has not only a PPIase activity but also a chaperone-like activity, which includes protein refolding and aggregation suppressing activities with regard to protein folding intermediates. Mutational analysis revealed that this chaperone-like activity was independent of the PPIase activity, and that the insertion sequence in the region corresponding to the flap seemed to be important. Three-dimensional structure of this FKBP showed that the insertion in the flap makes a domain which has a hydrophobic surface. Coexpression of aggregation prone proteins with these archaeal FKBPs were shown to improve their expression in soluble fraction in Escherichia coli. Fusion protein of the archaeal FKBP and an aggregation prone protein also show improved expression of the latter in E. coli.
肽脯氨酰顺反异构酶(PPIases)在生物体内广泛存在。虽然在真核生物和细菌(真细菌)中已对三类PPIases,即亲环蛋白(CyP)、FK506结合蛋白(FKBP)和小菌素(Pvn)进行了详细研究,但对于古菌的PPIases却知之甚少。在古菌中发现的13种亲环蛋白中,只有嗜盐菌亲环蛋白(HbsCyP19)得到了表征。这是一种对环孢菌素A(CsA)敏感的亲环蛋白,分子量为19.4 kDa。在培养基中盐浓度较高时,HbsCyP19的PPIase活性和对CsA的敏感性更高。除了共生嗜泉古菌中的一个同源物外,在古菌中未发现其他小菌素。在古菌中发现了两种类型的FKBP,即26 - 30 kDa的长型和17 - 18 kDa的短型FKBP。截至目前,已发现12种短型FKBP和18种长型FKBP。短型FKBP和长型FKBP的N端序列彼此相似,且与人类FKBP12(HsFKBP12)具有同源性。然而,它们在与HsFKBP12的凸起和襟翼环相对应的区域有两个插入序列。长型古菌FKBP在其C端区域还有约100个氨基酸序列。来自嗜热栖热甲烷球菌的一种短型古菌FKBP不仅具有PPIase活性,还具有伴侣样活性,包括对蛋白质折叠中间体的蛋白质重折叠和聚集抑制活性。突变分析表明,这种伴侣样活性独立于PPIase活性,并且在与襟翼相对应区域的插入序列似乎很重要。这种FKBP的三维结构表明,襟翼中的插入形成了一个具有疏水表面的结构域。已证明将易于聚集的蛋白质与这些古菌FKBP共表达可提高它们在大肠杆菌可溶性部分中的表达。古菌FKBP与易于聚集的蛋白质的融合蛋白在大肠杆菌中也显示出后者表达的改善。