ID   NXB2_CERLA              Reviewed;          55 AA.
AC   P01526;
DT   21-JUL-1986, integrated into UniProtKB/Swiss-Prot.
DT   21-JUL-1986, sequence version 1.
DT   03-AUG-2022, entry version 70.
DE   RecName: Full=Neurotoxin B-II;
OS   Cerebratulus lacteus (Milky ribbon worm) (Micrura lactea).
OC   Eukaryota; Metazoa; Spiralia; Lophotrochozoa; Nemertea; Pilidiophora;
OC   Heteronemertea; Lineidae; Cerebratulus.
OX   NCBI_TaxID=6221;
RN   [1]
RP   PROTEIN SEQUENCE, HYDROXYLATION AT PRO-10, AND DISULFIDE BONDS.
RX   PubMed=7263698; DOI=10.1016/s0021-9258(19)52508-x;
RA   Blumenthal K.M., Keim P.S., Heinrikson R.L., Kem W.R.;
RT   "Structure and action of heteronemertine polypeptide toxins. Amino acid
RT   sequence of Cerebratulus lacteus toxin B-II and revised structure of toxin
RT   B-IV.";
RL   J. Biol. Chem. 256:9063-9067(1981).
CC   -!- FUNCTION: This toxin increases the excitability of nerves by delaying
CC       the inactivation of the voltage-gated sodium channel (Nav). Only acts
CC       on some crustacean (By similarity). Neurotoxin B-II is less abundant,
CC       but 15-fold more toxic than neurotoxin B-VI. {ECO:0000250}.
CC   -!- SUBCELLULAR LOCATION: Secreted.
CC   -!- SIMILARITY: Belongs to the worm B-toxin family. {ECO:0000305}.
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DR   PIR; A01789; NTHNB2.
DR   AlphaFoldDB; P01526; -.
DR   SMR; P01526; -.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0019871; F:sodium channel inhibitor activity; IEA:InterPro.
DR   GO; GO:0090729; F:toxin activity; IEA:UniProtKB-KW.
DR   Gene3D; 1.10.287.120; -; 1.
DR   InterPro; IPR012497; Neurotoxin_B-IV.
DR   InterPro; IPR036586; Neurotoxin_B-IV-like_sf.
DR   Pfam; PF07822; Toxin_13; 1.
DR   SUPFAM; SSF57011; SSF57011; 1.
PE   1: Evidence at protein level;
KW   Direct protein sequencing; Disulfide bond; Hydroxylation;
KW   Ion channel impairing toxin; Secreted; Toxin;
KW   Voltage-gated sodium channel impairing toxin.
FT   CHAIN           1..55
FT                   /note="Neurotoxin B-II"
FT                   /id="PRO_0000221571"
FT   MOD_RES         10
FT                   /note="Hydroxyproline"
FT                   /evidence="ECO:0000269|PubMed:7263698"
FT   DISULFID        12..48
FT                   /evidence="ECO:0000269|PubMed:7263698"
FT   DISULFID        16..52
FT                   /evidence="ECO:0000269|PubMed:7263698"
FT   DISULFID        23..41
FT                   /evidence="ECO:0000269|PubMed:7263698"
FT   DISULFID        26..37
FT                   /evidence="ECO:0000269|PubMed:7263698"
SQ   SEQUENCE   55 AA;  6028 MW;  0918C1D1FB2FA904 CRC64;
     ASSTWGGSYP ACENNCRKQY DDCIKCQGKW AGKRGKCAAH CAVQTTSCND KCKKH