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

Plant Cyclophilins: Multifaceted Proteins With Versatile Roles

Cyclophilins constitute a family of ubiquitous proteins that bind cyclosporin A (CsA), an immunosuppressant drug. Several of these proteins possess peptidyl-prolyl cis-trans isomerase (PPIase) activity that catalyzes the cis-trans isomerization of the peptide bond preceding a proline residue, essential for correct folding of the proteins. Compared to prokaryotes and other eukaryotes studied until now, the cyclophilin gene families in plants exhibit considerable expansion. With few exceptions, the role of the majority of these proteins in plants is still a matter of conjecture. However, recent studies suggest that cyclophilins are highly versatile proteins with multiple functionalities, and regulate a plethora of growth and development processes in plants, ranging from hormone signaling to the stress response. The present review discusses the implications of cyclophilins in different facets of cellular processes, particularly in the context of plants, and provides a glimpse into the molecular mechanisms by which these proteins fine-tune the diverse physiological pathways.

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.

Transcriptional analysis of the cyclophilin A gene (cypA) of Streptomyces chrysomallus

Streptomyces chrysomallus produces a 17.5-kDa cyclophilin (CypA) as a major cytosolic protein. Northern blotting of total RNA from S. chrysomallus showed that cypA is transcribed as a monocistronic 500-nt transcript during the vegetative growth phase only. Consistently, Western blot analysis and enzyme activity determinations revealed a high level of CypA which declined drastically when cultures entered postexponential phase. Primer extension experiments revealed that cypA is transcribed as a leaderless transcript with the startpoint of transcription and translation being the same AUG codon. Analysis of -10 and -35 regions revealed an EohrdB-specific promoter consensus sequence in accordance with the observed transcription during vegetative growth of cultures. The leaderless cypA mRNA sequence between codons 5 to 12 shows complementarity to an internal antidownstream box of 16S rRNA of Streptomyces lividans. This may indicate a possible interaction of the leaderless cypA transcript with the 16S mRNA in translation initiation.

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.