ID   PSPB_CANLF              Reviewed;         363 AA.
AC   P17129;
DT   01-AUG-1990, integrated into UniProtKB/Swiss-Prot.
DT   01-AUG-1990, sequence version 1.
DT   25-MAY-2022, entry version 118.
DE   RecName: Full=Pulmonary surfactant-associated protein B;
DE            Short=SP-B;
DE   AltName: Full=6 kDa protein;
DE   AltName: Full=Pulmonary surfactant protein 18;
DE            Short=SP 18;
DE   AltName: Full=Pulmonary surfactant-associated proteolipid SPL(Phe);
DE   Flags: Precursor; Fragment;
GN   Name=SFTPB; Synonyms=SFTP3;
OS   Canis lupus familiaris (Dog) (Canis familiaris).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi; Mammalia;
OC   Eutheria; Laurasiatheria; Carnivora; Caniformia; Canidae; Canis.
OX   NCBI_TaxID=9615;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA], AND PROTEIN SEQUENCE OF 182-211.
RC   TISSUE=Lung;
RX   PubMed=3467361; DOI=10.1073/pnas.84.1.66;
RA   Hawgood S., Benson B.J., Schilling J., Damm D., Clements J.A., White R.T.;
RT   "Nucleotide and amino acid sequences of pulmonary surfactant protein SP 18
RT   and evidence for cooperation between SP 18 and SP 28-36 in surfactant lipid
RT   adsorption.";
RL   Proc. Natl. Acad. Sci. U.S.A. 84:66-70(1987).
CC   -!- FUNCTION: Pulmonary surfactant-associated proteins promote alveolar
CC       stability by lowering the surface tension at the air-liquid interface
CC       in the peripheral air spaces. SP-B increases the collapse pressure of
CC       palmitic acid to nearly 70 millinewtons per meter.
CC   -!- SUBUNIT: Homodimer; disulfide-linked.
CC   -!- SUBCELLULAR LOCATION: Secreted, extracellular space, surface film.
CC   -!- MISCELLANEOUS: Pulmonary surfactant consists of 90% lipid and 10%
CC       protein. There are 4 surfactant-associated proteins: 2 collagenous,
CC       carbohydrate-binding glycoproteins (SP-A and SP-D) and 2 small
CC       hydrophobic proteins (SP-B and SP-C).
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DR   EMBL; M15170; AAA30893.1; -; mRNA.
DR   PIR; B29072; A29072.
DR   AlphaFoldDB; P17129; -.
DR   SMR; P17129; -.
DR   InParanoid; P17129; -.
DR   Proteomes; UP000002254; Unplaced.
DR   GO; GO:0097208; C:alveolar lamellar body; IBA:GO_Central.
DR   GO; GO:0005615; C:extracellular space; IBA:GO_Central.
DR   GO; GO:0005771; C:multivesicular body; IBA:GO_Central.
DR   GO; GO:0006629; P:lipid metabolic process; IEA:InterPro.
DR   GO; GO:0007585; P:respiratory gaseous exchange by respiratory system; IEA:UniProtKB-KW.
DR   InterPro; IPR003119; SAP_A.
DR   InterPro; IPR007856; SapB_1.
DR   InterPro; IPR008138; SapB_2.
DR   InterPro; IPR011001; Saposin-like.
DR   InterPro; IPR008139; SaposinB_dom.
DR   Pfam; PF02199; SapA; 1.
DR   Pfam; PF05184; SapB_1; 1.
DR   Pfam; PF03489; SapB_2; 2.
DR   SMART; SM00162; SAPA; 1.
DR   SMART; SM00741; SapB; 3.
DR   SUPFAM; SSF47862; SSF47862; 3.
DR   PROSITE; PS51110; SAP_A; 1.
DR   PROSITE; PS50015; SAP_B; 3.
PE   1: Evidence at protein level;
KW   Direct protein sequencing; Disulfide bond; Gaseous exchange; Glycoprotein;
KW   Reference proteome; Repeat; Secreted; Signal; Surface film.
FT   SIGNAL          <1..16
FT                   /evidence="ECO:0000255"
FT   PROPEP          17..180
FT                   /id="PRO_0000031644"
FT   CHAIN           181..259
FT                   /note="Pulmonary surfactant-associated protein B"
FT                   /id="PRO_0000031645"
FT   PROPEP          260..363
FT                   /id="PRO_0000031646"
FT   DOMAIN          18..58
FT                   /note="Saposin A-type"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00414"
FT   DOMAIN          58..140
FT                   /note="Saposin B-type 1"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   DOMAIN          184..261
FT                   /note="Saposin B-type 2"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   DOMAIN          277..352
FT                   /note="Saposin B-type 3"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   CARBOHYD        293
FT                   /note="N-linked (GlcNAc...) asparagine"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   DISULFID        62..136
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   DISULFID        65..130
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   DISULFID        93..105
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   DISULFID        188..257
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   DISULFID        191..251
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   DISULFID        215..226
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   DISULFID        228
FT                   /note="Interchain"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   DISULFID        281..348
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   DISULFID        284..342
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   DISULFID        307..317
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00415"
FT   NON_TER         1
SQ   SEQUENCE   363 AA;  40180 MW;  F4DAD0E02D8B2719 CRC64;
     LLWLLLLPTL CGLGAADWSA PSLACARGPA FWCQSLEQAL QCRALGHCLQ EVWGNARADD
     LCQECQDIVR ILTKMTKEAI FQDMVRKFLE HECDVLPLKL LTPQCHHMLG TYFPVVVDYF
     QSQINPKIIC KHLGLCKPGL PEPEQESELS DPLLDKLILP ELPGALQVTG PHTQDLSEQQ
     LPIPLPYCWL CRTLIKRIQA MIPKGVLAVT VGQVCHVVPL VVGGICQCLG ERYTVLLLDA
     LLGRMLPQLV CGLVLRCSHE DSAGPALASL PSEWSPQESK CQLCMFVTTQ AGNHSEQATP
     QAIRQACLSS WLDRQKCEQF VEQHMPRLQT LASGGRDAHT TCQALGACRT TFSPLQCIHI
     PHF