ID   LIMU_LIMPO              Reviewed;          84 AA.
AC   P02744;
DT   21-JUL-1986, integrated into UniProtKB/Swiss-Prot.
DT   21-JUL-1986, sequence version 1.
DT   03-AUG-2022, entry version 79.
DE   RecName: Full=Limulin;
DE   Flags: Fragment;
OS   Limulus polyphemus (Atlantic horseshoe crab).
OC   Eukaryota; Metazoa; Ecdysozoa; Arthropoda; Chelicerata; Merostomata;
OC   Xiphosura; Limulidae; Limulus.
OX   NCBI_TaxID=6850;
RN   [1]
RP   PROTEIN SEQUENCE.
RX   PubMed=409430; DOI=10.1021/bi00638a026;
RA   Kaplan R., Li S.S.-L., Kehoe J.M.;
RT   "Molecular characterization of limulin, a sialic acid binding lectin from
RT   the hemolymph of the horseshoe crab, Limulus polyphemus.";
RL   Biochemistry 16:4297-4303(1977).
CC   -!- FUNCTION: This is a lectin that binds sialic acid.
CC   -!- COFACTOR:
CC       Name=Ca(2+); Xref=ChEBI:CHEBI:29108; Evidence={ECO:0000305};
CC       Note=Binds 2 calcium ions per subunit. {ECO:0000305};
CC   -!- SUBUNIT: Homopentamer. Pentraxin (or pentaxin) have a discoid
CC       arrangement of 5 non-covalently bound subunits.
CC   -!- DOMAIN: A possible carbohydrate binding site is located between
CC       positions 14 and 20.
CC   -!- PTM: A disulfide bond links Cys-38 to a Cys in the C-terminal half of
CC       the chain of 163 residues.
CC   -!- SIMILARITY: Belongs to the pentraxin family. {ECO:0000305}.
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DR   PIR; A03204; LSHC.
DR   GO; GO:0030246; F:carbohydrate binding; IEA:UniProtKB-KW.
DR   GO; GO:0046872; F:metal ion binding; IEA:UniProtKB-KW.
DR   InterPro; IPR013320; ConA-like_dom_sf.
DR   InterPro; IPR001759; Pentraxin-related.
DR   Pfam; PF00354; Pentaxin; 1.
DR   SUPFAM; SSF49899; SSF49899; 1.
DR   PROSITE; PS51828; PTX_2; 1.
PE   1: Evidence at protein level;
KW   Calcium; Direct protein sequencing; Disulfide bond; Lectin; Metal-binding.
FT   CHAIN           1..>84
FT                   /note="Limulin"
FT                   /id="PRO_0000162503"
FT   DOMAIN          6..>84
FT                   /note="Pentraxin (PTX)"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU01172"
FT   BINDING         67
FT                   /ligand="Ca(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29108"
FT                   /ligand_label="1"
FT                   /evidence="ECO:0000255"
FT   BINDING         68
FT                   /ligand="Ca(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29108"
FT                   /ligand_label="1"
FT                   /evidence="ECO:0000255"
FT   DISULFID        38..?
FT   NON_TER         84
SQ   SEQUENCE   84 AA;  9530 MW;  00E17AD002B6048B CRC64;
     LEEGEITSKV KFPPSSSPSF PRLVMVGTLP DLQEITLCYW FKVNQLKGTL GHSRVLBMFS
     YATAKKDNEL LTFLDEQGDF LFNV