ID   3SBB_HEMHA              Reviewed;          37 AA.
AC   P0DQH4;
DT   05-JUN-2019, integrated into UniProtKB/Swiss-Prot.
DT   05-JUN-2019, sequence version 1.
DT   25-MAY-2022, entry version 7.
DE   RecName: Full=Hemextin B {ECO:0000303|PubMed:16204244};
DE   AltName: Full=Hemachatus extrinsic tenase inhibitor B {ECO:0000303|PubMed:16204244};
DE   Flags: Fragment;
OS   Hemachatus haemachatus (Rinkhals) (Sepedon haemachatus).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
OC   Lepidosauria; Squamata; Bifurcata; Unidentata; Episquamata; Toxicofera;
OC   Serpentes; Colubroidea; Elapidae; Elapinae; Hemachatus.
OX   NCBI_TaxID=8626;
RN   [1]
RP   PROTEIN SEQUENCE, SUBCELLULAR LOCATION, FUNCTION, MASS SPECTROMETRY, AND
RP   SUBUNIT.
RC   TISSUE=Venom;
RX   PubMed=16204244; DOI=10.1074/jbc.m508987200;
RA   Banerjee Y., Mizuguchi J., Iwanaga S., Kini R.M.;
RT   "Hemextin AB complex, a unique anticoagulant protein complex from
RT   Hemachatus haemachatus (African Ringhals cobra) venom that inhibits clot
RT   initiation and factor VIIa activity.";
RL   J. Biol. Chem. 280:42601-42611(2005).
RN   [2]
RP   ERRATUM OF PUBMED:16204244.
RA   Banerjee Y., Mizuguchi J., Iwanaga S., Kini R.M.;
RL   J. Biol. Chem. 281:22427-22427(2006).
RN   [3]
RP   SUBUNIT.
RC   TISSUE=Venom;
RX   PubMed=17704148; DOI=10.1529/biophysj.106.100164;
RA   Banerjee Y., Lakshminarayanan R., Vivekanandan S., Anand G.S.,
RA   Valiyaveettil S., Kini R.M.;
RT   "Biophysical characterization of anticoagulant hemextin AB complex from the
RT   venom of snake Hemachatus haemachatus.";
RL   Biophys. J. 93:3963-3976(2007).
CC   -!- FUNCTION: Hemextin B (monomer): does not show anticoagulant activity.
CC       Seems only to synergitically enhance hemextin A activity.
CC       {ECO:0000269|PubMed:16204244}.
CC   -!- FUNCTION: Hemextin AB complex: specifically inhibits the activation of
CC       FX (F10) by the TF-FVIIa complex (extrinsic tenase complex (ETC))
CC       (IC(50)= 100 nM, Ki=50 nM) by non-competitively inhibiting the
CC       enzymatic activity of FVIIa. {ECO:0000269|PubMed:16204244}.
CC   -!- SUBUNIT: Heterotetramer composed of 2 hemextin A and 2 hemextin B
CC       chains; non-covalently linked. Does not exists as a complex in the
CC       crude venom. {ECO:0000269|PubMed:16204244,
CC       ECO:0000269|PubMed:17704148}.
CC   -!- SUBCELLULAR LOCATION: Secreted {ECO:0000269|PubMed:16204244}.
CC   -!- TISSUE SPECIFICITY: Expressed by the venom gland. {ECO:0000305}.
CC   -!- PTM: May contain several disulfide bonds. {ECO:0000305}.
CC   -!- MASS SPECTROMETRY: Mass=6792.56; Method=Electrospray;
CC       Evidence={ECO:0000269|PubMed:16204244};
CC   -!- SIMILARITY: Belongs to the snake three-finger toxin family. Short-chain
CC       subfamily. Type IB cytotoxin sub-subfamily. {ECO:0000305}.
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DR   AlphaFoldDB; P0DQH4; -.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0090729; F:toxin activity; IEA:UniProtKB-KW.
PE   1: Evidence at protein level;
KW   Blood coagulation cascade inhibiting toxin; Direct protein sequencing;
KW   Disulfide bond; Hemostasis impairing toxin; Secreted; Toxin.
FT   CHAIN           1..>37
FT                   /note="Hemextin B"
FT                   /evidence="ECO:0000269|PubMed:16204244"
FT                   /id="PRO_0000447302"
FT   NON_TER         37
SQ   SEQUENCE   37 AA;  4323 MW;  3464247DBB688B77 CRC64;
     LKCKNKVVPF LKCKNKVVPF LCYKMTLKKV TPKIKRG