# PPIB

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/PPIB
> Markdown URL: https://mediated.wiki/source/PPIB.md
> Source: https://en.wikipedia.org/wiki/PPIB
> Source revision: 1317914686
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

{{Short description|Protein-coding gene in the species Homo sapiens}}
{{Infobox_gene}}
'''Peptidyl-prolyl cis-trans isomerase B''' is an [enzyme](/source/enzyme) that is encoded by the ''PPIB'' [gene](/source/gene).<ref name="pmid2000394">{{cite journal | vauthors = Price ER, Zydowsky LD, Jin MJ, Baker CH, McKeon FD, Walsh CT | title = Human cyclophilin B: a second cyclophilin gene encodes a peptidyl-prolyl isomerase with a signal sequence | journal = Proc Natl Acad Sci U S A | volume = 88 | issue = 5 | pages = 1903–7 | date = Apr 1991 | pmid = 2000394 | pmc = 51134 | doi = 10.1073/pnas.88.5.1903 | bibcode = 1991PNAS...88.1903P | doi-access = free }}</ref>  As a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family, this protein catalyzes the [cis-trans](/source/cis-trans) [isomerization](/source/isomerization) of proline imidic [peptide bond](/source/peptide_bond)s, which allows it to regulate protein folding of [type I collagen](/source/type_I_collagen).<ref name = "pmid1530810">{{cite journal | vauthors = Kazui T, Inoue N, Yamada O, Komatsu S | title = Selective cerebral perfusion during operation for aneurysms of the aortic arch: a reassessment | journal = The Annals of Thoracic Surgery | volume = 53 | issue = 1 | pages = 109–14 | date = Jan 1992 | pmid = 1530810 | doi=10.1016/0003-4975(92)90767-x| doi-access = free }}</ref><ref name = "pmid24713575">{{cite journal | vauthors = Hoffmann H, Schiene-Fischer C | title = Functional aspects of extracellular cyclophilins | journal = Biological Chemistry | volume = 395 | issue = 7–8 | pages = 721–35 | date = Jul 2014 | pmid = 24713575 | doi = 10.1515/hsz-2014-0125 | s2cid = 32395688 }}</ref> Generally, PPIases are found in all [eubacteria](/source/eubacteria) and [eukaryotes](/source/eukaryotes), as well as in a few [archaebacteria](/source/archaebacteria), and thus are highly conserved.

== Structure ==

Like other [cyclophilin](/source/cyclophilin)s, PPIB forms a β-barrel structure with a [hydrophobic](/source/hydrophobic) core. This β-barrel is composed of eight anti-parallel [β-strand](/source/%CE%B2-strand)s and capped by two [α-helices](/source/%CE%B1-helices) at the top and bottom. In addition, the β-turns and loops in the strands contribute to the flexibility of the barrel.<ref name="pmid15963461">{{cite journal | vauthors = Wang T, Yun CH, Gu SY, Chang WR, Liang DC | title = 1.88 A crystal structure of the C domain of hCyP33: a novel domain of peptidyl-prolyl cis-trans isomerase | journal = Biochemical and Biophysical Research Communications | volume = 333 | issue = 3 | pages = 845–9 | date = Aug 2005 | pmid = 15963461 | doi = 10.1016/j.bbrc.2005.06.006 | bibcode = 2005BBRC..333..845W }}</ref> In particular, PPIB is a 21 kDa protein which contains a [C-terminal](/source/C-terminal) ER retention motif that directs the protein to the ER [organelle](/source/organelle), while its [N-terminal](/source/N-terminal) extension attaches it to its [substrates](/source/substrate_(biochemistry)).<ref name = "pmid24713575"/><ref name="pmid157064402">{{cite journal|date=Mar 2005|title=Roles of cyclophilins in cancers and other organ systems|journal=World Journal of Surgery|volume=29|issue=3|pages=276–80|doi=10.1007/s00268-004-7812-7|pmid=15706440|vauthors=Yao Q, Li M, Yang H, Chai H, Fisher W, Chen C|s2cid=11678319}}</ref>

== Function ==
PPIB is a member of the peptidyl-prolyl cis-trans isomerase ([PPIase](/source/Prolyl_isomerase)) family. PPIases catalyze the [cis-trans isomerization of proline imidic peptide bonds](/source/Proline) and regulate protein folding and maturation. Proline is the only amino acid known to exist in both the ''cis'' and ''trans'' isomerization rate ''in vivo'', and is often the rate-limiting step in protein refolding.<ref>{{Cite journal|last1=Göthel|first1=S. F.|last2=Marahiel|first2=M. A.|date=March 1999|title=Peptidyl-prolyl cis-trans isomerases, a superfamily of ubiquitous folding catalysts|journal=Cellular and Molecular Life Sciences|volume=55|issue=3|pages=423–436|doi=10.1007/s000180050299|issn=1420-682X|pmid=10228556|s2cid=24868224|pmc=11146858}}</ref> The PPIase family is further divided into three structurally distinct subfamilies: [cyclophilin](/source/cyclophilin) (CyP), FK506-binding protein ([FKBP](/source/FKBP)), and [parvulin](/source/parvulin) (Pvn).<ref name="pmid153081022">{{cite journal|date=Jan 1992|title=Selective cerebral perfusion during operation for aneurysms of the aortic arch: a reassessment|journal=The Annals of Thoracic Surgery|volume=53|issue=1|pages=109–14|doi=10.1016/0003-4975(92)90767-x|pmid=1530810|vauthors=Kazui T, Inoue N, Yamada O, Komatsu S|doi-access=free}}</ref><ref name="pmid159634612">{{cite journal|date=Aug 2005|title=1.88 A crystal structure of the C domain of hCyP33: a novel domain of peptidyl-prolyl cis-trans isomerase|journal=Biochemical and Biophysical Research Communications|volume=333|issue=3|pages=845–9|doi=10.1016/j.bbrc.2005.06.006|pmid=15963461|vauthors=Wang T, Yun CH, Gu SY, Chang WR, Liang DC |bibcode=2005BBRC..333..845W }}</ref> While each family demonstrates PPIase activity, the families have no sequence of structural similarities. As a cyclophilin, PPIB binds [cyclosporin A](/source/cyclosporin_A) (CsA) and can be found within the cell or secreted by the cell.<ref name="pmid157064402"/><ref name="pmid2471357522">{{cite journal|date=Jul 2014|title=Functional aspects of extracellular cyclophilins|journal=Biological Chemistry|volume=395|issue=7–8|pages=721–35|doi=10.1515/hsz-2014-0125|pmid=24713575|vauthors=Hoffmann H, Schiene-Fischer C|s2cid=32395688}}</ref>

== Human PPIB ==

PPIB is the second of 18 cyclophilins to be identified in humans, after CypA.<ref name="pmid153081022"/><ref name="pmid2471357522"/> PPIB localizes to the [endoplasmic reticulum](/source/endoplasmic_reticulum) (ER) and participates in many biological processes, including mitochondrial [metabolism](/source/metabolism), [apoptosis](/source/apoptosis), [redox](/source/redox), and [inflammation](/source/inflammation), as well as in related diseases and conditions, such as [ischemic reperfusion injury](/source/ischemic_reperfusion_injury), [AIDS](/source/AIDS), and [cancer](/source/cancer).<ref name="pmid157064402"/><ref name="pmid224848122">{{cite journal|date=May 2012|title=Comparing human pancreatic cell secretomes by in vitro aptamer selection identifies cyclophilin B as a candidate pancreatic cancer biomarker|journal=The Journal of Clinical Investigation|volume=122|issue=5|pages=1734–41|doi=10.1172/JCI62385|pmc=3336995|pmid=22484812|vauthors=Ray P, Rialon-Guevara KL, Veras E, Sullenger BA, White RR}}</ref>  It is also associated with viral infections. In eukaryotes, cyclophilins localize ubiquitously to many cell and tissue types.<ref name="pmid157064402"/><ref name="pmid15963461" /> In addition to PPIase and protein [chaperone](/source/chaperone_(protein)) activities, cyclophilins function in [mitochondria](/source/mitochondria)l metabolism, [apoptosis](/source/apoptosis), immunological response, [inflammation](/source/inflammation), and [cell growth](/source/cell_growth) and proliferation.<ref name="pmid1530810" /><ref name="pmid157064402"/><ref name="pmid15963461" /> Along with [PPIC](/source/PPIC), PPIB localizes to the [endoplasmic reticulum](/source/endoplasmic_reticulum) (ER), where it maintains [redox](/source/redox) homeostasis. Depletion of these two cyclophilins leads to hyperoxidation of the ER.<ref name="pmid24990953">{{cite journal | vauthors = Stocki P, Chapman DC, Beach LA, Williams DB | title = Depletion of cyclophilins B and C leads to dysregulation of endoplasmic reticulum redox homeostasis | journal = The Journal of Biological Chemistry | volume = 289 | issue = 33 | pages = 23086–96 | date = Aug 2014 | pmid = 24990953 | doi = 10.1074/jbc.M114.570911 | pmc=4132807| doi-access = free }}</ref>

In the ER, PPIB interacts with proteins such as P3H1, CRTAP, BiP, GRP94, PDI, and calreticulin to form foldase and chaperone complexes and facilitate protein folding, especially for type I collagen.<ref name = "pmid24968150">{{cite journal | vauthors = Cabral WA, Perdivara I, Weis M, Terajima M, Blissett AR, Chang W, Perosky JE, Makareeva EN, Mertz EL, Leikin S, Tomer KB, Kozloff KM, Eyre DR, Yamauchi M, Marini JC | title = Abnormal type I collagen post-translational modification and crosslinking in a cyclophilin B KO mouse model of recessive osteogenesis imperfecta | journal = PLOS Genetics | volume = 10 | issue = 6 | article-number = e1004465 | date = Jun 2014 | pmid = 24968150 | doi = 10.1371/journal.pgen.1004465 | pmc=4072593 | doi-access = free }}</ref><ref name = "pmid24043621">{{cite journal | vauthors = Ishikawa Y, Bächinger HP | title = An additional function of the rough endoplasmic reticulum protein complex prolyl 3-hydroxylase 1·cartilage-associated protein·cyclophilin B: the CXXXC motif reveals disulfide isomerase activity in vitro | journal = The Journal of Biological Chemistry | volume = 288 | issue = 44 | pages = 31437–46 | date = Nov 2013 | pmid = 24043621 | doi = 10.1074/jbc.M113.498063 | pmc=3814740| doi-access = free }}</ref> This protein is the major PPIase for type I collagen, since the collagen contains an abundance of prolines that require cis-trans isomerization for proper folding. Thus, PPIB is essential for collagen biosynthesis and post-translational modification and affects fibril assembly, matrix cross-linking, and bone mineralization.<ref name = "pmid24968150"/>

In addition, it is associated with the secretory pathway and released in biological fluids. This protein can bind to cells derived from T- and B-lymphocytes, and may regulate cyclosporine A-mediated immunosuppression.<ref name="entrez">{{cite web | title = Entrez Gene: PPIB peptidylprolyl isomerase B (cyclophilin B)| url = https://www.ncbi.nlm.nih.gov/gene?Db=gene&Cmd=ShowDetailView&TermToSearch=5479}}</ref> In one experiment, the addition of PPIB into cell cultures in vitro induced [chemotaxis](/source/chemotaxis) and [integrin](/source/integrin)-mediated adhesion of T cells to the [extracellular matrix](/source/extracellular_matrix) (ECM), suggesting that it might function in [innate immunity](/source/innate_immunity) by recruiting T cells into infected tissue in vivo.<ref name="pmid157064402"/>

== Clinical significance ==

As a cyclophilin, PPIB binds the immunosuppressive drug CsA to form a CsA-cyclophilin complex, which then targets [calcineurin](/source/calcineurin) to inhibit the signaling pathway for T-cell activation.

In cardiac myogenic cells, cyclophilins have been observed to be activated by heat shock and [hypoxia](/source/hypoxia_(medical))-reoxygenation as well as complex with [heat shock protein](/source/heat_shock_protein)s. Thus, cyclophilins may function in cardioprotection during ischemia-reperfusion injury.<ref name="pmid157064402"/>

PPIB contributes to the replication and infection of viruses causing diseases such as [AIDS](/source/AIDS), [hepatitis C](/source/hepatitis_C), [measles](/source/measles), and [influenza A](/source/influenza_A). Thus, therapeutic targeting of PPIB with selective inhibitors may prove effective in combating viral infections and inflammation.<ref name = "pmid24713575"/> Currently, PPIB is employed as a biomarker for various types of cancer.<ref name="pmid224848122"/> Moreover, there are two [antigen](/source/antigen)ic [epitopes](/source/epitopes) (CypB84-92 and CypB91-99) recognized by HLA-A24-restricted and tumor-specific [cytotoxic T lymphocyte](/source/cytotoxic_T_lymphocyte)s which could be used as cancer [vaccine](/source/vaccine)s, and in fact, were used to treat [lung cancer](/source/lung_cancer) in a clinical trial.<ref name="pmid157064402"/>

== Bacterial PPIB ==
PPIB has been identified in both [Gram-negative bacteria](/source/Gram-negative_bacteria) and [Gram-positive bacteria](/source/Gram-positive_bacteria) as an intracellular protein. In ''[Escherichia coli](/source/Escherichia_coli)'', PPIB has been shown to have both [PPIase](/source/PPIase) activity and [Chaperone (protein)](/source/Chaperone_(protein)) activity.<ref>{{Cite journal|last1=Skagia|first1=Aggeliki|last2=Vezyri|first2=Eleni|last3=Sigala|first3=Markezina|last4=Kokkinou|first4=Areti|last5=Karpusas|first5=Michael|last6=Venieraki|first6=Anastasia|last7=Katinakis|first7=Panagiotis|last8=Dimou|first8=Maria|date=January 2017|title=Structural and functional analysis of cyclophilin PpiB mutants supports an in vivo function not limited to prolyl isomerization activity|journal=Genes to Cells: Devoted to Molecular & Cellular Mechanisms|volume=22|issue=1|pages=32–44|doi=10.1111/gtc.12452|issn=1365-2443|pmid=27868330|doi-access=free}}</ref> In ''[Staphylococcus aureus](/source/Staphylococcus_aureus)'', PPIB has been shown to have PPIase activity, and to directly assist in the refolding of [Staphylococcal nuclease](/source/Micrococcal_nuclease).<ref>{{Cite journal|last1=Wiemels|first1=Richard E.|last2=Cech|first2=Stephanie M.|last3=Meyer|first3=Nikki M.|last4=Burke|first4=Caleb A.|last5=Weiss|first5=Andy|last6=Parks|first6=Anastacia R.|last7=Shaw|first7=Lindsey N.|last8=Carroll|first8=Ronan K.|date=2017-01-01|title=An Intracellular Peptidyl-Prolyl cis/trans Isomerase Is Required for Folding and Activity of the Staphylococcus aureus Secreted Virulence Factor Nuclease|journal=Journal of Bacteriology|volume=199|issue=1|doi=10.1128/JB.00453-16|issn=1098-5530|pmc=5165095|pmid=27795319}}</ref> Aside from these bacteria, PPIB has been identified in ''Brucella abortus'', ''[Mycobacterium tuberculosis](/source/Mycobacterium_tuberculosis)'', ''[Bacillus subtilis](/source/Bacillus_subtilis)'' and other bacteria.<ref>{{Cite journal|last1=Roset|first1=Mara S.|last2=García Fernández|first2=Lucía|last3=DelVecchio|first3=Vito G.|last4=Briones|first4=Gabriel|date=February 2013|title=Intracellularly Induced Cyclophilins Play an Important Role in Stress Adaptation and Virulence of Brucella abortus|journal=Infection and Immunity|volume=81|issue=2|pages=521–530|doi=10.1128/IAI.01125-12|issn=0019-9567|pmc=3553818|pmid=23230297}}</ref><ref>{{Cite journal|last1=Göthel|first1=S. F.|last2=Scholz|first2=C.|last3=Schmid|first3=F. X.|last4=Marahiel|first4=M. A.|date=1998-09-22|title=Cyclophilin and trigger factor from Bacillus subtilis catalyze in vitro protein folding and are necessary for viability under starvation conditions|journal=Biochemistry|volume=37|issue=38|pages=13392–13399|doi=10.1021/bi981253w|issn=0006-2960|pmid=9748346}}</ref><ref>{{Cite journal|last1=Pandey|first1=Saurabh|last2=Sharma|first2=Ashish|last3=Tripathi|first3=Deeksha|last4=Kumar|first4=Ashutosh|last5=Khubaib|first5=Mohd|last6=Bhuwan|first6=Manish|last7=Chaudhuri|first7=Tapan Kumar|last8=Hasnain|first8=Seyed Ehtesham|last9=Ehtesham|first9=Nasreen Zafar|date=2016-03-16|title=Mycobacterium tuberculosis Peptidyl-Prolyl Isomerases Also Exhibit Chaperone like Activity In-Vitro and In-Vivo|journal=PLOS ONE|volume=11|issue=3|article-number=e0150288|doi=10.1371/journal.pone.0150288|issn=1932-6203|pmc=4794191|pmid=26981873|bibcode=2016PLoSO..1150288P|doi-access=free}}</ref>

== Interactions ==

PPIB has been shown to [interact](/source/Protein-protein_interaction) with:
* [Apolipoprotein B](/source/Apolipoprotein_B).<ref name=pmid12397072>{{cite journal | vauthors = Zhang J, Herscovitz H | title = Nascent lipidated apolipoprotein B is transported to the Golgi as an incompletely folded intermediate as probed by its association with network of endoplasmic reticulum molecular chaperones, GRP94, ERp72, BiP, calreticulin, and cyclophilin B | journal = J. Biol. Chem. | volume = 278 | issue = 9 | pages = 7459–68 | date = Feb 2003 | pmid = 12397072 | doi = 10.1074/jbc.M207976200 | doi-access = free }}</ref>
* [P3H1](/source/P3H1),<ref name = "pmid24043621"/> 
* [CRTAP](/source/CRTAP),<ref name = "pmid24043621"/>
* [BiP](/source/Binding_immunoglobulin_protein),<ref name = "pmid24968150"/> 
* [GRP94](/source/GRP94),<ref name = "pmid24968150"/> 
* [PDI](/source/Protein_disulfide-isomerase),<ref name = "pmid24968150"/> and 
* [calreticulin](/source/calreticulin).<ref name = "pmid24968150"/> 
{{Clear}}

== References ==
{{reflist|33em}}

== Further reading ==
{{refbegin|33em}}
* {{cite journal | vauthors = Rasmussen HH, van Damme J, Puype M, Gesser B, Celis JE, Vandekerckhove J | title = Microsequences of 145 proteins recorded in the two-dimensional gel protein database of normal human epidermal keratinocytes. | journal = Electrophoresis | volume = 13 | issue = 12 | pages = 960–9 | year = 1993 | pmid = 1286667 | doi = 10.1002/elps.11501301199 | s2cid = 41855774 }}
* {{cite journal | vauthors = Peddada LB, McPherson JD, Law R, Wasmuth JJ, Youderian P, Deans RJ | title = Somatic cell mapping of the human cyclophilin B gene (PPIB) to chromosome 15. | journal = Cytogenet. Cell Genet. | volume = 60 | issue = 3–4 | pages = 219–21 | year = 1992 | pmid = 1505219 | doi = 10.1159/000133343 }}
* {{cite journal | vauthors = Arber S, Krause KH, Caroni P | title = s-cyclophilin is retained intracellularly via a unique COOH-terminal sequence and colocalizes with the calcium storage protein calreticulin | journal = J. Cell Biol. | volume = 116 | issue = 1 | pages = 113–25 | year = 1992 | pmid = 1530944 | pmc = 2289259 | doi = 10.1083/jcb.116.1.113 }}
* {{cite journal | vauthors = Hasel KW, Glass JR, Godbout M, Sutcliffe JG | title = An endoplasmic reticulum-specific cyclophilin | journal = Mol. Cell. Biol. | volume = 11 | issue = 7 | pages = 3484–91 | year = 1991 | pmid = 1710767 | pmc = 361082 | doi =  10.1128/mcb.11.7.3484}}
* {{cite journal | vauthors = Spik G, Haendler B, Delmas O, Mariller C, Chamoux M, Maes P, Tartar A, Montreuil J, Stedman K, Kocher HP | title = A novel secreted cyclophilin-like protein (SCYLP) | journal = J. Biol. Chem. | volume = 266 | issue = 17 | pages = 10735–8 | year = 1991 | doi = 10.1016/S0021-9258(18)99078-2 | pmid = 2040592 | doi-access = free }}
* {{cite journal | vauthors = Bram RJ, Crabtree GR | title = Calcium signalling in T cells stimulated by a cyclophilin B-binding protein | journal = Nature | volume = 371 | issue = 6495 | pages = 355–8 | year = 1994 | pmid = 7522304 | doi = 10.1038/371355a0 | bibcode = 1994Natur.371..355B | s2cid = 4318545 }}
* {{cite journal | vauthors = Allain F, Boutillon C, Mariller C, Spik G | title = Selective assay for CyPA and CyPB in human blood using highly specific anti-peptide antibodies | journal = J. Immunol. Methods | volume = 178 | issue = 1 | pages = 113–20 | year = 1995 | pmid = 7829860 | doi = 10.1016/0022-1759(94)00249-V }}
* {{cite journal | vauthors = Price ER, Jin M, Lim D, Pati S, Walsh CT, McKeon FD | title = Cyclophilin B trafficking through the secretory pathway is altered by binding of cyclosporin A | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 91 | issue = 9 | pages = 3931–5 | year = 1994 | pmid = 7909608 | pmc = 43696 | doi = 10.1073/pnas.91.9.3931 | bibcode = 1994PNAS...91.3931P | doi-access = free }}
* {{cite journal | vauthors = Mikol V, Kallen J, Walkinshaw MD | title = X-ray structure of a cyclophilin B/cyclosporin complex: comparison with cyclophilin A and delineation of its calcineurin-binding domain | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 91 | issue = 11 | pages = 5183–6 | year = 1994 | pmid = 8197205 | pmc = 43956 | doi = 10.1073/pnas.91.11.5183 | bibcode = 1994PNAS...91.5183M | doi-access = free }}
* {{cite journal | vauthors = Allain F, Denys A, Spik G | title = Characterization of surface binding sites for cyclophilin B on a human tumor T-cell line | journal = J. Biol. Chem. | volume = 269 | issue = 24 | pages = 16537–40 | year = 1994 | doi = 10.1016/S0021-9258(19)89421-8 | pmid = 8206968 | doi-access = free }}
* {{cite journal | vauthors = Luban J, Bossolt KL, Franke EK, Kalpana GV, Goff SP | title = Human immunodeficiency virus type 1 Gag protein binds to cyclophilins A and B | journal = Cell | volume = 73 | issue = 6 | pages = 1067–78 | year = 1993 | pmid = 8513493 | doi = 10.1016/0092-8674(93)90637-6 | s2cid = 38546328 }}
* {{cite journal | vauthors = Braaten D, Ansari H, Luban J | title = The hydrophobic pocket of cyclophilin is the binding site for the human immunodeficiency virus type 1 Gag polyprotein | journal = J. Virol. | volume = 71 | issue = 3 | pages = 2107–13 | year = 1997 | doi = 10.1128/JVI.71.3.2107-2113.1997 | pmid = 9032343 | pmc = 191305 }}
* {{cite journal | vauthors = Montague JW, Hughes FM, Cidlowski JA | title = Native recombinant cyclophilins A, B, and C degrade DNA independently of peptidylprolyl cis-trans-isomerase activity. Potential roles of cyclophilins in apoptosis | journal = J. Biol. Chem. | volume = 272 | issue = 10 | pages = 6677–84 | year = 1997 | pmid = 9045699 | doi = 10.1074/jbc.272.10.6677 | doi-access = free }}
* {{cite journal | vauthors = Denys A, Allain F, Foxwell B, Spik G | title = Distribution of cyclophilin B-binding sites in the subsets of human peripheral blood lymphocytes | journal = Immunology | volume = 91 | issue = 4 | pages = 609–17 | year = 1997 | pmid = 9378502 | pmc = 1363883 | doi = 10.1046/j.1365-2567.1997.00296.x }}
* {{cite journal | vauthors = Endrich MM, Gehring H | title = The V3 loop of human immunodeficiency virus type-1 envelope protein is a high-affinity ligand for immunophilins present in human blood | journal = Eur. J. Biochem. | volume = 252 | issue = 3 | pages = 441–6 | year = 1998 | pmid = 9546659 | doi = 10.1046/j.1432-1327.1998.2520441.x | doi-access = free }}
* {{cite journal | vauthors = Endrich MM, Gehrig P, Gehring H | title = Maturation-induced conformational changes of HIV-1 capsid protein and identification of two high affinity sites for cyclophilins in the C-terminal domain | journal = J. Biol. Chem. | volume = 274 | issue = 9 | pages = 5326–32 | year = 1999 | pmid = 10026140 | doi = 10.1074/jbc.274.9.5326 | doi-access = free }}
* {{cite journal | vauthors = Bristow R, Byrne J, Squirell J, Trencher H, Carter T, Rodgers B, Saman E, Duncan J | title = Human cyclophilin has a significantly higher affinity for HIV-1 recombinant p55 than p24 | journal = J. Acquir. Immune Defic. Syndr. Hum. Retrovirol. | volume = 20 | issue = 4 | pages = 334–6 | year = 1999 | pmid = 10096576 | doi = 10.1097/00042560-199904010-00002 | doi-access = free }}
* {{cite journal | vauthors = Rycyzyn MA, Reilly SC, O'Malley K, Clevenger CV | title = Role of cyclophilin B in prolactin signal transduction and nuclear retrotranslocation | journal = Mol. Endocrinol. | volume = 14 | issue = 8 | pages = 1175–86 | year = 2001 | pmid = 10935542 | doi = 10.1210/mend.14.8.0508 | doi-access = free }}
* {{cite journal | vauthors = Yurchenko V, O'Connor M, Dai WW, Guo H, Toole B, Sherry B, Bukrinsky M | title = CD147 is a signaling receptor for cyclophilin B | journal = Biochem. Biophys. Res. Commun. | volume = 288 | issue = 4 | pages = 786–8 | year = 2001 | pmid = 11688976 | doi = 10.1006/bbrc.2001.5847 | bibcode = 2001BBRC..288..786Y }}
{{refend}}

== External links ==
* {{PDBe-KB2|P23284|Peptidyl-prolyl cis-trans isomerase B}}

{{PDB Gallery|geneid=5479}}

---
Adapted from the Wikipedia article [PPIB](https://en.wikipedia.org/wiki/PPIB) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/PPIB?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.