Cloning and characterization of ppiB, a Bacillus subtilis gene which encodes a cyclosporin A-sensitive peptidyl-prolyl cis-trans isomerase

iTRAQ-based quantitative proteomics analysis of the effect of ACT001 on non-alcoholic steatohepatitis in mice

ACT001 is a novel sesquiterpene lactone derivative that has been shown to have significant antitumor and anti-inflammatory effects. However, the effect of ACT001 on nonalcoholic steatohepatitis (NASH) is unknown. Methionine and choline deficient (MCD) diet induced NASH model in C57BL/6J mice. Steatosis, inflammation and fibrosis-related indices of serum and liver tissues were detected by fully automated biochemical analyzer, enzyme-linked immunosorbent assay (ELISA) kit, flow cytometry, hematoxylin and eosin (H&E), Masson and immunohistochemical staining. The results showed that ACT001 reduced serum lipid and inflammatory factor levels, attenuated hepatic steatosis, inflammation and fibrosis, and inhibited hepatic oxidative stress and activation of NOD-like receptor protein 3 (NLRP3) inflammatory vesicles in NASH mice. In addition, 381 differentially expressed proteins (DEPs), including 162 up-regulated and 219 down-regulated proteins, were identified in the MCD group and ACT001 high-dose group using isotope labeling relative and absolute quantification (iTRAQ) technique analysis. Among these DEPs, five proteins associated with NAFLD were selected for real-time fluorescence quantitative PCR (RT-qPCR) validation, and the results were consistent with proteomics. In conclusion, ACT001 has a therapeutic effect on NASH, and the results of proteomic analysis will provide new ideas for the mechanism study of ACT001 for NASH treatment.

Targeting Protein Folding: A Novel Approach for the Treatment of Pathogenic Bacteria

Infectious diseases are a major cause of morbidity and mortality worldwide, exacerbated by increasing antibiotic resistance in many bacterial species. The development of drugs with new modes of action is essential. A leading strategy is antivirulence, with the aim to target bacterial proteins that are important in disease causation and progression but do not affect growth, resulting in reduced selective pressure for resistance. Immunophilins, a superfamily of peptidyl-prolyl cis-trans isomerase (PPIase) enzymes have been shown to be important for virulence in a broad-spectrum of pathogenic bacteria. This Perspective will provide an overview of the recent advances made in understanding the role of each immunophilin family, cyclophilins, FK506 binding proteins (FKBPs), and parvulins in bacteria. Inhibitor design and medicinal chemistry strategies for development of novel drugs against bacterial FKBPs will be discussed. Furthermore, drugs against human cyclophilins and parvulins will be reviewed in their current indication as antiviral and anticancer therapies.

Microbial cyclophilins: specialized functions in virulence and beyond

Cyclophilins belong to the superfamily of peptidyl-prolyl cis/trans isomerases (PPIases, EC: 5.2.1.8), the enzymes that catalyze the cis/trans isomerization of peptidyl-prolyl peptide bonds in unfolded and partially folded polypeptide chains and native state proteins. Cyclophilins have been extensively studied, since they are involved in multiple cellular processes related to human pathologies, such as neurodegenerative disorders, infectious diseases, and cancer. However, the presence of cyclophilins in all domains of life indicates a broader biological importance. In this mini-review, we summarize current advances in the study of microbial cyclophilins. Apart from their anticipated role in protein folding and chaperoning, cyclophilins are involved in several other biological processes, such as cellular signal transduction, adaptation to stress, control of pathogens virulence, and modulation of host immune response. Since many existing family members do not have well-defined functions and novel ones are being characterized, the requirement for further studies on their biological role and molecular mechanism of action is apparent.

An Intracellular Peptidyl-Prolyl cis/trans Isomerase Is Required for Folding and Activity of the Staphylococcus aureus Secreted Virulence Factor Nuclease

Staphylococcus aureus is an important human pathogen that relies on a large repertoire of secreted and cell wall-associated proteins for pathogenesis. Consequently, the ability of the organism to cause disease is absolutely dependent on its ability to synthesize and successfully secrete these proteins. In this study, we investigate the role of peptidyl-prolyl cis/trans isomerases (PPIases) on the activity of the S. aureus secreted virulence factor nuclease (Nuc). We identify a staphylococcal cyclophilin-type PPIase (PpiB) that is required for optimal activity of Nuc. Disruption of ppiB results in decreased nuclease activity in culture supernatants; however, the levels of Nuc protein are not altered, suggesting that the decrease in activity results from misfolding of Nuc in the absence of PpiB. We go on to demonstrate that PpiB exhibits PPIase activity in vitro, is localized to the bacterial cytosol, and directly interacts with Nuc in vitro to accelerate the rate of Nuc refolding. Finally, we demonstrate an additional role for PpiB in S. aureus hemolysis and demonstrate that the S. aureus parvulin-type PPIase PrsA also plays a role in the activity of secreted virulence factors. The deletion of prsA leads to a decrease in secreted protease and phospholipase activity, similar to that observed in other Gram-positive pathogens. Together, these results demonstrate, for the first time to our knowledge, that PPIases play an important role in the secretion of virulence factors in S. aureus IMPORTANCE: Staphylococcus aureus is a highly dangerous bacterial pathogen capable of causing a variety of infections throughout the human body. The ability of S. aureus to cause disease is largely due to an extensive repertoire of secreted and cell wall-associated proteins, including adhesins, toxins, exoenzymes, and superantigens. These virulence factors, once produced, are typically transported across the cell membrane by the secretory (Sec) system in a denatured state. Consequently, once outside the cell, they must refold into their active form. This step often requires the assistance of bacterial folding proteins, such as PPIases. In this work, we investigate the role of PPIases in S. aureus and uncover a cyclophilin-type enzyme that assists in the folding/refolding of staphylococcal nuclease.

Microbial peptidyl-prolyl cis/trans isomerases (PPIases): virulence factors and potential alternative drug targets

Initially discovered in the context of immunomodulation, peptidyl-prolyl cis/trans isomerases (PPIases) were soon identified as enzymes catalyzing the rate-limiting protein folding step at peptidyl bonds preceding proline residues. Intense searches revealed that PPIases are a superfamily of proteins consisting of three structurally distinguishable families with representatives in every described species of prokaryote and eukaryote and, recently, even in some giant viruses. Despite the clear-cut enzymatic activity and ubiquitous distribution of PPIases, reports on solely PPIase-dependent biological roles remain scarce. Nevertheless, they have been found to be involved in a plethora of biological processes, such as gene expression, signal transduction, protein secretion, development, and tissue regeneration, underscoring their general importance. Hence, it is not surprising that PPIases have also been identified as virulence-associated proteins. The extent of contribution to virulence is highly variable and dependent on the pleiotropic roles of a single PPIase in the respective pathogen. The main objective of this review is to discuss this variety in virulence-related bacterial and protozoan PPIases as well as the involvement of host PPIases in infectious processes. Moreover, a special focus is given to Legionella pneumophila macrophage infectivity potentiator (Mip) and Mip-like PPIases of other pathogens, as the best-characterized virulence-related representatives of this family. Finally, the potential of PPIases as alternative drug targets and first tangible results are highlighted.

Preclinical characterization of naturally occurring polyketide cyclophilin inhibitors from the sanglifehrin family

Cyclophilin inhibitors currently in clinical trials for hepatitis C virus (HCV) are all analogues of cyclosporine (CsA). Sanglifehrins are a group of naturally occurring cyclophilin binding polyketides that are structurally distinct from the cyclosporines and are produced by a microorganism amenable to biosynthetic engineering for lead optimization and large-scale production by fermentation. Preclinical characterization of the potential utility of this class of compounds for the treatment of HCV revealed that the natural sanglifehrins A to D are all more potent than CsA at disrupting formation of the NS5A-CypA, -CypB, and -CypD complexes and at inhibition of CypA, CypB, and CypD isomerase activity. In particular, sanglifehrin B (SfB) was 30- to 50-fold more potent at inhibiting the isomerase activity of all Cyps tested than CsA and was also shown to be a more potent inhibitor of the 1b subgenomic replicon (50% effective concentrations [EC50s] of 0.070 μM and 0.16 μM in Huh 5-2 and Huh 9-13 cells, respectively). Physicochemical and mouse pharmacokinetic analyses revealed low oral bioavailability (F<4%) and low solubility (<25 μM), although the half-lives (t1/2) of SfA and SfB in mouse blood after intravenous (i.v.) dosing were long (t1/2>5 h). These data demonstrate that naturally occurring sanglifehrins are suitable lead compounds for the development of novel analogues that are less immunosuppressive and that have improved metabolism and pharmacokinetic properties.

Actinobacteria cyclophilins: phylogenetic relationships and description of new class- and order-specific paralogues

Cyclophilins are folding helper enzymes belonging to the class of peptidyl-prolyl cis-trans isomerases (PPIases; EC 5.2.1.8) that catalyze the cis-trans isomerization of peptidyl-prolyl bonds in proteins. They are ubiquitous proteins present in almost all living organisms analyzed to date, with extremely rare exceptions. Few cyclophilins have been described in Actinobacteria, except for three reported in the genus Streptomyces and another one in Mycobacterium tuberculosis. In this study, we performed a complete phylogenetic analysis of all Actinobacteria cyclophilins available in sequence databases and new Streptomyces cyclophilin genes sequenced in our laboratory. Phylogenetic analyses of cyclophilins recovered six highly supported groups of paralogy. Streptomyces appears as the bacteria having the highest cyclophilin diversity, harboring proteins from four groups. The first group was named "A" and is made up of highly conserved cytosolic proteins of approximately 18 kDa present in all Actinobacteria. The second group, "B," includes cytosolic proteins widely distributed throughout the genus Streptomyces and closely related to eukaryotic cyclophilins. The third group, "M" cyclophilins, consists of high molecular mass cyclophilins ( approximately 30 kDa) that contain putative membrane binding domains and would constitute the only membrane cyclophilins described to date in bacteria. The fourth group, named "C" cyclophilins, is made up of proteins of approximately 18 kDa that are orthologous to Gram-negative proteobacteria cyclophilins. Ancestral character reconstruction under parsimony was used to identify shared-derived (and likely functionally important) amino acid residues of each paralogue. Southern and Western blot experiments were performed to determine the taxonomic distribution of the different cyclophilins in Actinobacteria.

Cloning and characterization of a Streptomyces antibioticus ATCC11891 cyclophilin related to Gram negative bacteria cyclophilins

Cyclophilins are folding helper enzymes and represent a family of the enzyme class of peptidyl-prolyl cis-trans isomerases. Here, we report the molecular cloning and biochemical characterization of SanCyp18, an 18-kDa cyclophilin from Streptomyces antibioticus ATCC11891 located in the cytoplasm and constitutively expressed during development. Amino acid sequence analysis revealed a much higher homology to cyclophilins from Gram negative bacteria than to known cyclophilins from Streptomyces or other Gram positive bacteria. SanCyp18 is inhibited weakly by CsA, with a K(i) value of 21 microM, similar to cyclophilins from Gram negative bacteria. However, this value is more than 20-fold higher than the K(i) values reported for cyclophilins from other Gram positive bacteria, which makes SanCyp18 unique within this group. The presence of SanCyp18 in Streptomyces is likely due to horizontal gene transmission from Gram-negative bacteria to Streptomyces.

Regulation of peptide bond cis/trans isomerization by enzyme catalysis and its implication in physiological processes

In some cases, the slow rotational movement underlying peptide bond cis/trans isomerizations is found to control the biological activity of proteins. Peptide bond cis/trans isomerases as cyclophilins, Fk506-binding proteins, parvulins, and bacterial hsp70 generally assist in the interconversion of the polypeptide substrate cis/trans isomers, and rate acceleration is the dominating mechanism of action in cells. We present evidence disputing the hypothesis that some of the molecular properties of these proteins play an auxiliary role in enzyme function.

Striking complexity of lipopolysaccharide defects in a collection of Sinorhizobium meliloti mutants

Although the role that lipopolysaccharide (LPS) plays in the symbiosis between Sinorhizobium meliloti and alfalfa has been studied for over a decade, its function in this process remains controversial and poorly understood. This is largely due to a lack of mutants affected by its synthesis. In one of the definitive studies concerning this issue, Clover et al. (R. H. Clover, J. Kieber, and E. R. Signer, J. Bacteriol. 171:3961-3967, 1989) identified a series of mutants with putative LPS defects, judged them to be symbiotically proficient on Medicago sativa, and concluded that LPS might not have a symbiotic function in S. meliloti. The mutations in these strains were never characterized at the molecular level nor was the LPS from most of them analyzed. We have transduced these mutations from the Rm2011 background from which they were originally isolated into the sequenced strain Rm1021 and have characterized the resulting strains in greater detail. We found the LPS from these mutants to display a striking complexity of phenotypes on polyacrylamide electrophoresis gels, including additional rough LPS bands and alterations in the molecular weight distribution of the smooth LPS. We found that some of the mutants contain insertions in genes that are predicted to be involved in the synthesis of carbohydrate components of LPS, including ddhB, lpsB, lpsC, and lpsE. The majority, however, code for proteins predicted to be involved in a wide variety of functions not previously recognized to play a role in LPS synthesis, including a possible transcription elongation factor (GreA), a possible queuine synthesis protein, and a possible chemotaxis protein. Furthermore, using more extensive assays, we have found that most of these strains have symbiotic deficiencies. These results support more recent findings that alterations in LPS structure can affect the ability of S. meliloti to form an effective symbiosis.

Cyclophilin A regulates HIV-1 infectivity, as demonstrated by gene targeting in human T cells

The human immunodeficiency virus type 1 (HIV-1) Gag polyprotein binds most members of the cyclophilin family of peptidyl-prolyl isomerases. Of 15 known human cyclophilins, cyclophilin A (CypA) has been the focus of investigation because it was detected in HIV-1 virions. To determine whether CypA promotes HIV-1 replication, we deleted the gene encoding CypA (PPIA) in human CD4(+) T cells by homologous recombination. HIV-1 replication in PPIA(-/-) cells was decreased and not inhibited further by cyclosporin or gag mutations that disrupt Gag's interaction with cyclophilins, indicating that no other cyclophilin family members promote HIV-1 replication. The defective replication phenotype was specific for wild-type HIV-1 since HIV-2/SIV isolates, as well as HIV-1 bearing a gag mutation that confers cyclosporin resistance, replicated the same in PPIA(+/+) and PPIA(-/-) cells. Stable re-expression of CypA in PPIA(-/-) cells restored HIV-1 replication to an extent that correlated with steady-state levels of CypA. Finally, virions from PPIA(-/-) cells possessed no obvious biochemical abnormalities but were less infectious than virions from wild-type cells. These data formally demonstrate that CypA regulates the infectivity of HIV-1 virions.

Isolation, characterization and targeted disruption of mouse ppia: cyclophilin A is not essential for mammalian cell viability

Cyclophilins (CyPs) are a family of proteins found in organisms ranging from prokaryotes to humans. These molecules exhibit peptidyl-prolyl isomerase activity in vitro, suggesting that they influence the conformation of proteins in cells. CyPs also bind with varying affinities to the immunosuppressive drug cyclosporin A (CsA), a compound used clinically to prevent allograft rejection. The founding member of the family, cyclophilin A (CyPA), is an abundant, ubiquitously expressed protein of unknown function that binds with nanomolar affinity to CsA. Here, we describe the isolation and characterization of mouse Ppia (mPpia), the gene encoding CyPA. Ppia was isolated using a PCR screen that distinguishes the expressed gene from multiple pseudogenes present in the mouse genome. mPpia consists of 5 exons and 4 introns spanning roughly 4.5 kb and maps to chromosome 11 near the centromere. Sequence analysis of a 369-bp fragment from the proximal promoter region of mPpia revealed the presence of a TATA box and sites recognized by several transcriptional regulators, including Sp1, AP-2, GATA factors, c-Myb, and NF-IL-6. This region is sufficient to drive high-level reporter gene expression in transfected cells. Both copies of Ppia were disrupted in murine embryonic stem (ES) cells via gene targeting. Ppia(-/-) ES cells grow normally and differentiate into hematopoeitic precursor cells in vitro, indicating that CyPA is not essential for mammalian cell viability.

Gene for a cyclophilin-type peptidyl-prolyl cis-trans isomerase from a halophilic archaeum, Halobacterium cutirubrum

A gene encoding a cyclophilin (CyP)-type peptidyl prolyl cis-trans isomerase (PPIase) was cloned from a halophilic archaeum, Halobacterium cutirubrum DSM 669, and sequenced. Although amino-acid residues common to CyPs were conserved, an insertion that showed no homology to other CyPs was found in its N-terminal region. Sequence analysis revealed that the amino-acid sequence of this CyP was 40-45% identical to those of eukaryotes and Bacillus subtilis with high cyclosporin A sensitivity, but 27% identical to those of cyclosporin A-insensitive PPIases of Escherichia coli. The gene was also expressed in E. coli. The activity of purified recombinant CyP-type PPIase was stimulated by the addition of KCl, and was suppressed by cyclosporin A.

Histidine 109 in peptidyl-prolyl cis-trans isomerase of Bacillus subtilis plays an important role in catalysis and in cyclosporin A binding

The cyclophilin of Bacillus subtilis has a moderate affinity to cyclosporin A (IC50: 120 nM) and low catalytic activity (Kcat/ Km: 1.1 microM-1 s-1) when compared to other ubiquitous peptidyl-prolyl cis-trans isomerases (PPIases). The active site residues V52, H90 and H109, which are not conserved within other peptidyl-prolyl cis-trans isomerases, were found to play an important role in cyclosporin A binding and catalytic activity. In this work we report on double mutations of these residues, which greatly improved cyclosporin A affinity and catalytic activity. The H90N/H109W mutation displayed an IC50 value of 46 nM whereas the V52M/H109F mutation exhibited over 18-fold higher catalytic activity than that detected for wild-type PPIase. The mutations H109W and H109F of the B. subtilis PPIase showed no change in cyclosporin A affinity and catalytic activity between pH 6 and 8. In contrast, wild-type PPIase (H109) showed up to 10-fold reduction below pH 7.5, both in cyclosporin A affinity and in catalytic activity. These findings clearly underline the importance of the unique H109 residue in the B. subtilis enzyme.

An internal FK506-binding domain is the catalytic core of the prolyl isomerase activity associated with the Bacillus subtilis trigger factor

Two major families of peptidylprolyl cis-trans-isomerases, the cyclophilins and the structurally unrelated FK506-binding proteins (FKBPs), have been identified as cellular factors involved in protein folding in vitro. Here we report on the biochemical characterization of a second prolyl isomerase of Bacillus subtilis that was purified from a cyclophilin-negative (ppiB null) mutant and was shown to be the trigger factor (TigBS). N-terminal sequencing of 27 amino acid residues of the purified protein revealed 100% identity to the deduced sequence encoded by the tig gene, sequenced as a part of the B. subtilis genome project. The tigBS gene, located at 246 degrees on the genetic map upstream of the clpX and lonA,B genes, encodes an acidic protein (pI 4.3) of 47.5 kDa. Purified and recombinant TigBS-His proteins share the same substrate specificity and catalytic activity (Kcat/K(m) of 1.5 microM-1 s-1); both are inhibited by the macrolide FK506 with IC50 the range of 500 nM. We also demonstrate that the prolyl isomerase activity of TigBS is mediated by an internal domain of about 13 kDa (homologous to FKPB12) that represents the catalytic core of the trigger factor.

ScCypB is a novel second cytosolic cyclophilin from Streptomyces chrysomallus which is phylogenetically distant from ScCypA

A novel second streptomycete cyclophilin gene-designated sccypB-was isolated from a cosmid gene library of Streptomyces chrysomallus by using as gene probe a fragment of the previously isolated cyclophilin gene sccypA of the same organism. From its sequence the gene sccypB should encode a protein of M(r) 18868. Expression of sccypB in Escherichia coli as a hexaHis-tagged fusion protein (H6ScCypB) and enzymic characterization of the purified protein showed that, like ScCypA, ScCypB is a peptidyl-prolyl cis-trans isomerase (PPIase). The specific activity and substrate specificity of the enzyme were comparable to that of ScCypA, but it was threefold less sensitive to inhibition by cyclosporin A (CsA). In contrast to ScCypA, which is abundant and exists in free and liganded form, ScCypB was 50- to 100-fold less abundant in cytosol-derived protein fractions of S. chrysomallus or Streptomyces lividans, as revealed by Western blot analyses, suggesting a specialized function for this enzyme in the streptomycete cell. Both sccypB and sccypA were found to be present as single copies in the genome of S. chrysomallus and hybridized to a single band in chromosomal DNAs of other streptomycetes. High-level expression of sccypB as well as of sccypA cloned into the expression vector pIJ702 did not produce detectable changes in growth and morphology of S. chrysomallus and S. lividans. Calculations of similarities to known cyclophilin sequences and construction of phylogenetic trees indicated that ScCypB and ScCypA are phylogenetically distant from each other. While ScCypA is clearly related to the eukaryotic cyclophilins, the analyses show the sequence of ScCypB to be the most divergent of all cyclophilin sequences, indicating that it possibly constitutes a cluster by itself.

Cold shock stress-induced proteins in Bacillus subtilis

Bacteria respond to a decrease in temperature with the induction of proteins that are classified as cold-induced proteins (CIPs). Using two-dimensional gel electrophoresis, we analyzed the cold shock response in Bacillus subtilis. After a shift from 37 to 15 degrees C the synthesis of a majority of proteins was repressed; in contrast, 37 proteins were synthesized at rates higher than preshift rates. One hour after cold shock, the induction of CIPs decreased, and after 2 h, general protein synthesis resumed. The identified main CIPs were excised from two-dimensional gels and were subjected to microsequencing. Three small acidic proteins that showed the highest relative induction after cold shock were highly homologous and belonged to a protein family of which one member, the major cold shock protein, CspB, has previously been characterized. Two-dimensional gel analyses of a cspB null mutant revealed that CspB affects the level of induction of several CIPs. Other identified CIPs function at various levels of cellular physiology, such as chemotaxis (CheY), sugar uptake (Hpr), translation (ribosomal proteins S6 and L7/L12), protein folding (PPiB), and general metabolism (CysK, Ilvc, Gap, and triosephosphate isomerase).

Advances in the use of Bacillus subtilis for the expression and secretion of heterologous proteins

During the past year, significant progress has been made using Bacillus subtilis to produce a wide range of foreign proteins. Through strain improvement and co-expression of molecular chaperones, secretory proteins can be produced at a higher level. Through protein engineering, target proteins can be redesigned to have better stability and solubility. A combination of these two strategies would be a useful approach to produce heterologous proteins from B. subtilis at high quality and with a high yield.

Compilation and analysis of Bacillus subtilis sigma A-dependent promoter sequences: evidence for extended contact between RNA polymerase and upstream promoter DNA

Sequence analysis of 236 promoters recognized by the Bacillus subtilis sigma A-RNA polymerase reveals an extended promoter structure. The most highly conserved bases include the -35 and -10 hexanucleotide core elements and a TG dinucleotide at position -15, -14. In addition, several weakly conserved A and T residues are present upstream of the -35 region. Analysis of dinucleotide composition reveals A2- and T2-rich sequences in the upstream promoter region (-36 to -70) which are phased with the DNA helix: An tracts are common near -43, -54 and -65; Tn tracts predominate at the intervening positions. When compared with larger regions of the genome, upstream promoter regions have an excess of An and Tn sequences for n > 4. These data indicate that an RNA polymerase binding site affects DNA sequence as far upstream as -70. This sequence conservation is discussed in light of recent evidence that the alpha subunits of the polymerase core bind DNA and that the promoter may wrap around RNA polymerase.

A cyclophilin from the polycentric anaerobic rumen fungus Orpinomyces sp. strain PC-2 is highly homologous to vertebrate cyclophilin B

A cyclophilin (CyP) purified to homogeneity from the polycentric anaerobic rumen fungus Orpinomyces sp. strain PC-2 had a molecular mass of 20.5 kDa and a pI of 8.1. The protein catalyzed the isomerization of the prolyl peptide bond of N-succinyl-Ala-Ala-(cis,trans)-Pro-Phe p-nitroanilide with a kcat/Km value of 9.3 x 10(6) M-1.s-1 at 10 degrees C and pH 7.8. Cyclosporin A strongly inhibited this peptidylprolyl cis-trans isomerase activity with an IC50 of 19.6 nM. The sequence of the first 30 N-terminal amino acids of this CyP had high homology with the N-terminal sequences of other eukaryotic CyPs. By use of a DNA hybridization probe amplified by PCR with degenerate oligonucleotide primers designed based on the amino acid sequences of the N terminus of this CyP and highly conserved internal regions of other CyPs, a full-length cDNA clone was isolated. It possessed an open reading frame encoding a polypeptide of 203 amino acids with a calculated molecular weight of 21,969, containing a putative hydrophobic signal peptide sequence of 22 amino acids preceding the N terminus of the mature enzyme and a C-terminal sequence, Lys-Ala-Glu-Leu, characteristic of an endoplasmic reticulum retention signal. The Orpinomyces PC-2 CyP is a typical type B CyP. The amino acid sequence of the Orpinomyces CyP exhibits striking degrees of identity with the corresponding human (70%), bovine (69%), mouse (68%), chicken (66%), maize (61%), and yeast (54%) proteins. Phylogenetic analysis based on the CyP sequences indicated that the evolutionary origin of the Orpinomyces CyP was closely related with CyPs of animals.