ID   3SLS_DENPO              Reviewed;          60 AA.
AC   P22947;
DT   01-AUG-1991, integrated into UniProtKB/Swiss-Prot.
DT   01-AUG-1991, sequence version 1.
DT   27-MAR-2024, entry version 88.
DE   RecName: Full=Calciseptin;
DE   AltName: Full=Calciseptine;
DE            Short=CaS;
DE   AltName: Full=L-type calcium channel blocker;
OS   Dendroaspis polylepis polylepis (Black mamba).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
OC   Lepidosauria; Squamata; Bifurcata; Unidentata; Episquamata; Toxicofera;
OC   Serpentes; Colubroidea; Elapidae; Elapinae; Dendroaspis.
OX   NCBI_TaxID=8620;
RN   [1]
RP   PROTEIN SEQUENCE, FUNCTION, AND SUBCELLULAR LOCATION.
RC   TISSUE=Venom;
RX   PubMed=1848702; DOI=10.1073/pnas.88.6.2437;
RA   de Weille J.R., Schweitz H., Maes P., Tartar A., Lazdunski M.;
RT   "Calciseptine, a peptide isolated from black mamba venom, is a specific
RT   blocker of the L-type calcium channel.";
RL   Proc. Natl. Acad. Sci. U.S.A. 88:2437-2440(1991).
RN   [2]
RP   SYNTHESIS.
RX   PubMed=1450521;
RA   Kuroda H., Chen Y.-N., Watanabe T.X., Kimura T., Sakakibara S.;
RT   "Solution synthesis of calciseptine, an L-type specific calcium channel
RT   blocker.";
RL   Pept. Res. 5:265-268(1992).
RN   [3]
RP   SYNTHESIS OF 41-48.
RX   PubMed=9636051; DOI=10.1021/bi9802723;
RA   Kini R.M., Caldwell R.A., Wu Q.Y., Baumgarten C.M., Feher J.J., Evans H.J.;
RT   "Flanking proline residues identify the L-type Ca2+ channel binding site of
RT   calciseptine and FS2.";
RL   Biochemistry 37:9058-9063(1998).
CC   -!- FUNCTION: This specific blocker of the L-type calcium channel
CC       (Cav1/CACNA1) is a smooth muscle relaxant and an inhibitor of cardiac
CC       contractions. {ECO:0000269|PubMed:1848702}.
CC   -!- SUBCELLULAR LOCATION: Secreted {ECO:0000269|PubMed:1848702}.
CC   -!- TISSUE SPECIFICITY: Expressed by the venom gland. {ECO:0000305}.
CC   -!- MISCELLANEOUS: The sensitivity is higher in cells of the cardiovascular
CC       system. Neuronal, and insulinoma cells L-type calcium channel are more
CC       resistant. A total resistance is found in skeletal muscle cells.
CC   -!- SIMILARITY: Belongs to the snake three-finger toxin family. Short-chain
CC       subfamily. L-type calcium blocker sub-subfamily. {ECO:0000305}.
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DR   PIR; A39165; A39165.
DR   PDB; 8WE7; EM; 3.20 A; B=1-60.
DR   PDB; 8WE8; EM; 2.90 A; B=1-60.
DR   PDBsum; 8WE7; -.
DR   PDBsum; 8WE8; -.
DR   AlphaFoldDB; P22947; -.
DR   SMR; P22947; -.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0005246; F:calcium channel regulator activity; IEA:UniProtKB-KW.
DR   GO; GO:0090729; F:toxin activity; IEA:UniProtKB-KW.
DR   Gene3D; 2.10.60.10; CD59; 1.
DR   InterPro; IPR045860; Snake_toxin-like_sf.
DR   InterPro; IPR018354; Snake_toxin_con_site.
DR   SUPFAM; SSF57302; Snake toxin-like; 1.
DR   PROSITE; PS00272; SNAKE_TOXIN; 1.
PE   1: Evidence at protein level;
KW   3D-structure; Calcium channel impairing toxin; Cardiotoxin;
KW   Direct protein sequencing; Disulfide bond; Ion channel impairing toxin;
KW   Secreted; Toxin; Voltage-gated calcium channel impairing toxin.
FT   CHAIN           1..60
FT                   /note="Calciseptin"
FT                   /evidence="ECO:0000269|PubMed:1848702"
FT                   /id="PRO_0000093667"
FT   REGION          41..48
FT                   /note="Important for binding to L-type calcium channels"
FT                   /evidence="ECO:0000269|PubMed:9636051"
FT   DISULFID        3..22
FT                   /evidence="ECO:0000250|UniProtKB:P0C1Z0"
FT   DISULFID        17..39
FT                   /evidence="ECO:0000250|UniProtKB:P0C1Z0"
FT   DISULFID        41..52
FT                   /evidence="ECO:0000250|UniProtKB:P0C1Z0"
FT   DISULFID        53..58
FT                   /evidence="ECO:0000250|UniProtKB:P0C1Z0"
SQ   SEQUENCE   60 AA;  7044 MW;  2F14B05972A40FFF CRC64;
     RICYIHKASL PRATKTCVEN TCYKMFIRTQ REYISERGCG CPTAMWPYQT ECCKGDRCNK
//