ID   CIRB_CHAPA              Reviewed;          31 AA.
AC   P56879; P82255;
DT   30-MAY-2000, integrated into UniProtKB/Swiss-Prot.
DT   05-DEC-2001, sequence version 2.
DT   25-MAY-2022, entry version 73.
DE   RecName: Full=Circulin-B;
DE            Short=CIRB;
OS   Chassalia parviflora.
OC   Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta;
OC   Spermatophyta; Magnoliopsida; eudicotyledons; Gunneridae; Pentapetalae;
OC   asterids; lamiids; Gentianales; Rubiaceae; Rubioideae; Palicoureeae;
OC   Chassalia.
OX   NCBI_TaxID=58431;
RN   [1]
RP   PROTEIN SEQUENCE.
RX   PubMed=4303114; DOI=10.1007/bf02138292;
RA   Hayashi K., Suketa Y., Suzuki T.;
RT   "Chemical structure of circulin B.";
RL   Experientia 24:656-657(1968).
RN   [2]
RP   PROTEIN SEQUENCE, AND MASS SPECTROMETRY.
RX   DOI=10.1021/ja00099a064;
RA   Gustafson K.R., Sowder R.C. II, Henderson L.E., Parson I.C., Kashman Y.,
RA   Cardellina J.H. Jr., McMahon J.B., Buckheit R.W. Jr., Pannell L.K.,
RA   Boyd M.R.;
RT   "Circulins A and B: novel HIV-inhibitor macrocyclic peptide from tropical
RT   tree Chassalia parvifolia.";
RL   J. Am. Chem. Soc. 116:9337-9338(1994).
RN   [3]
RP   DISULFIDE BONDS.
RX   PubMed=8920961; DOI=10.1006/bbrc.1996.1708;
RA   Derua R., Gustafson K.R., Pannell L.K.;
RT   "Analysis of the disulfide linkage pattern in circulin A and B, HIV-
RT   inhibitory macrocyclic peptides.";
RL   Biochem. Biophys. Res. Commun. 228:632-638(1996).
RN   [4]
RP   SYNTHESIS, AND ANTIBACTERIAL ACTIVITY.
RX   PubMed=10430870; DOI=10.1073/pnas.96.16.8913;
RA   Tam J.P., Lu Y.-A., Yang J.-L., Chiu K.-W.;
RT   "An unusual structural motif of antimicrobial peptides containing end-to-
RT   end macrocycle and cystine-knot disulfides.";
RL   Proc. Natl. Acad. Sci. U.S.A. 96:8913-8918(1999).
RN   [5]
RP   STRUCTURE BY NMR.
RA   Koltay A., Daly N.L., Gustafson K.R., Craik D.J.;
RT   "Structure of circulin B and implications for antimicrobial activity of the
RT   cyclotides.";
RL   Int. J. Pept. Protein Res. 11:99-106(2005).
CC   -!- FUNCTION: Probably participates in a plant defense mechanism. Has
CC       antibiotic activity. Inhibits the cytopathic effects and replication of
CC       the human immunodeficiency virus. Active against both Gram-positive and
CC       Gram-negative bacteria.
CC   -!- DOMAIN: The presence of a 'disulfide through disulfide knot'
CC       structurally defines this protein as a knottin.
CC   -!- PTM: This is a cyclic peptide.
CC   -!- MASS SPECTROMETRY: Mass=3284.7; Method=FAB;
CC       Evidence={ECO:0000269|Ref.2};
CC   -!- SIMILARITY: Belongs to the cyclotide family. Bracelet subfamily.
CC       {ECO:0000255|PROSITE-ProRule:PRU00395}.
CC   -!- CAUTION: This peptide is cyclic. The start position was chosen by
CC       similarity to OAK1 (kalata-B1) for which the DNA sequence is known.
CC       {ECO:0000305}.
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DR   PDB; 2ERI; NMR; -; A=5-31.
DR   PDBsum; 2ERI; -.
DR   AlphaFoldDB; P56879; -.
DR   SMR; P56879; -.
DR   EvolutionaryTrace; P56879; -.
DR   GO; GO:0042742; P:defense response to bacterium; IEA:UniProtKB-KW.
DR   InterPro; IPR005535; Cyclotide.
DR   InterPro; IPR012323; Cyclotide_bracelet_CS.
DR   InterPro; IPR036146; Cyclotide_sf.
DR   Pfam; PF03784; Cyclotide; 1.
DR   PIRSF; PIRSF037891; Cycloviolacin; 1.
DR   SUPFAM; SSF57038; SSF57038; 1.
DR   PROSITE; PS51052; CYCLOTIDE; 1.
DR   PROSITE; PS60008; CYCLOTIDE_BRACELET; 1.
PE   1: Evidence at protein level;
KW   3D-structure; Antibiotic; Antimicrobial; Direct protein sequencing;
KW   Disulfide bond; Knottin; Plant defense.
FT   PEPTIDE         1..31
FT                   /note="Circulin-B"
FT                   /id="PRO_0000044696"
FT   DISULFID        5..21
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00395,
FT                   ECO:0000269|PubMed:8920961"
FT   DISULFID        9..23
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00395,
FT                   ECO:0000269|PubMed:8920961"
FT   DISULFID        14..28
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00395,
FT                   ECO:0000269|PubMed:8920961"
FT   CROSSLNK        1..31
FT                   /note="Cyclopeptide (Gly-Asn)"
FT   STRAND          10..12
FT                   /evidence="ECO:0007829|PDB:2ERI"
FT   TURN            16..20
FT                   /evidence="ECO:0007829|PDB:2ERI"
FT   STRAND          22..24
FT                   /evidence="ECO:0007829|PDB:2ERI"
FT   STRAND          27..30
FT                   /evidence="ECO:0007829|PDB:2ERI"
SQ   SEQUENCE   31 AA;  3308 MW;  30C19A52F2EE13BB CRC64;
     GVIPCGESCV FIPCISTLLG CSCKNKVCYR N