ID   FIBL_BOMMO              Reviewed;         262 AA.
AC   P21828; Q17224;
DT   01-MAY-1991, integrated into UniProtKB/Swiss-Prot.
DT   01-MAY-1991, sequence version 1.
DT   25-MAY-2022, entry version 100.
DE   RecName: Full=Fibroin light chain;
DE            Short=Fib-L;
DE   AltName: Full=L-fibroin;
DE   Contains:
DE     RecName: Full=Fibroin light chain, short form;
DE   Flags: Precursor;
GN   Name=FIBL;
OS   Bombyx mori (Silk moth).
OC   Eukaryota; Metazoa; Ecdysozoa; Arthropoda; Hexapoda; Insecta; Pterygota;
OC   Neoptera; Endopterygota; Lepidoptera; Glossata; Ditrysia; Bombycoidea;
OC   Bombycidae; Bombycinae; Bombyx.
OX   NCBI_TaxID=7091;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA], PARTIAL PROTEIN SEQUENCE, AND ACETYLATION AT
RP   SER-19.
RC   STRAIN=J-139; TISSUE=Posterior silk gland;
RX   PubMed=2585514; DOI=10.1016/0022-2836(89)90295-7;
RA   Yamaguchi K., Kikuchi Y., Takagi T., Kikuchi A., Oyama F., Shimura K.,
RA   Mizuno S.;
RT   "Primary structure of the silk fibroin light chain determined by cDNA
RT   sequencing and peptide analysis.";
RL   J. Mol. Biol. 210:127-139(1989).
RN   [2]
RP   NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
RC   STRAIN=p50T;
RX   PubMed=15591204; DOI=10.1126/science.1102210;
RA   Xia Q., Zhou Z., Lu C., Cheng D., Dai F., Li B., Zhao P., Zha X., Cheng T.,
RA   Chai C., Pan G., Xu J., Liu C., Lin Y., Qian J., Hou Y., Wu Z., Li G.,
RA   Pan M., Li C., Shen Y., Lan X., Yuan L., Li T., Xu H., Yang G., Wan Y.,
RA   Zhu Y., Yu M., Shen W., Wu D., Xiang Z., Yu J., Wang J., Li R., Shi J.,
RA   Li H., Li G., Su J., Wang X., Li G., Zhang Z., Wu Q., Li J., Zhang Q.,
RA   Wei N., Xu J., Sun H., Dong L., Liu D., Zhao S., Zhao X., Meng Q., Lan F.,
RA   Huang X., Li Y., Fang L., Li C., Li D., Sun Y., Zhang Z., Yang Z.,
RA   Huang Y., Xi Y., Qi Q., He D., Huang H., Zhang X., Wang Z., Li W., Cao Y.,
RA   Yu Y., Yu H., Li J., Ye J., Chen H., Zhou Y., Liu B., Wang J., Ye J.,
RA   Ji H., Li S., Ni P., Zhang J., Zhang Y., Zheng H., Mao B., Wang W., Ye C.,
RA   Li S., Wang J., Wong G.K.-S., Yang H.;
RT   "A draft sequence for the genome of the domesticated silkworm (Bombyx
RT   mori).";
RL   Science 306:1937-1940(2004).
RN   [3]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RC   TISSUE=Posterior silk gland;
RX   PubMed=1347033; DOI=10.1016/0378-1119(92)90642-3;
RA   Kikuchi Y., Mori K., Suzuki S., Yamaguchi K., Mizuno S.;
RT   "Structure of the Bombyx mori fibroin light-chain-encoding gene: upstream
RT   sequence elements common to the light and heavy chain.";
RL   Gene 110:151-158(1992).
RN   [4]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA] OF 1-12.
RX   PubMed=1972197; DOI=10.1016/s0022-2836(05)80201-3;
RA   Hui C.C., Suzuki Y., Kikuchi Y., Mizuno S.;
RT   "Homeodomain binding sites in the 5' flanking region of the Bombyx mori
RT   silk fibroin light-chain gene.";
RL   J. Mol. Biol. 213:395-398(1990).
RN   [5]
RP   PROTEIN SEQUENCE OF 17-262, AND IDENTIFICATION BY MASS SPECTROMETRY.
RC   TISSUE=Silk gland;
RA   Lubec G., Chen W.-Q.;
RL   Submitted (AUG-2009) to UniProtKB.
RN   [6]
RP   INTERCHAIN DISULFIDE BOND.
RC   STRAIN=J-139;
RX   PubMed=10366732; DOI=10.1016/s0167-4838(99)00088-6;
RA   Tanaka K., Kajiyama N., Ishikura K., Waga S., Kikuchi A., Ohtomo K.,
RA   Takagi T., Mizuno S.;
RT   "Determination of the site of disulfide linkage between heavy and light
RT   chains of silk fibroin produced by Bombyx mori.";
RL   Biochim. Biophys. Acta 1432:92-103(1999).
RN   [7]
RP   SUBUNIT.
RX   PubMed=10986287; DOI=10.1074/jbc.m006897200;
RA   Inoue S., Tanaka K., Arisaka F., Kimura S., Ohtomo K., Mizuno S.;
RT   "Silk fibroin of Bombyx mori is secreted, assembling a high molecular mass
RT   elementary unit consisting of H-chain, L-chain, and p25, with a 6:6:1 molar
RT   ratio.";
RL   J. Biol. Chem. 275:40517-40528(2000).
CC   -!- FUNCTION: It is likely that the major role of L-chain is to prevent the
CC       retention of H-chain in ER by forming the disulfide linkage.
CC   -!- SUBUNIT: Silk fibroin elementary unit consists in a disulfide-linked
CC       heavy and light chain and a p25 glycoprotein in molar ratios of 6:6:1.
CC       This results in a complex of approximately 2.3 MDa.
CC       {ECO:0000269|PubMed:10986287}.
CC   -!- SUBCELLULAR LOCATION: Secreted.
CC   -!- TISSUE SPECIFICITY: Produced exclusively in the posterior (PSG) section
CC       of silk glands, which are essentially modified salivary glands.
CC   -!- PTM: The interchain disulfide bridge is essential for the intracellular
CC       transport and secretion of fibroin.
CC   -!- PTM: Partially N-terminally processed to yield a short form which lacks
CC       the first two residues of the long form.
CC   ---------------------------------------------------------------------------
CC   Copyrighted by the UniProt Consortium, see https://www.uniprot.org/terms
CC   Distributed under the Creative Commons Attribution (CC BY 4.0) License
CC   ---------------------------------------------------------------------------
DR   EMBL; X17291; CAA35180.1; -; mRNA.
DR   EMBL; CK545649; -; NOT_ANNOTATED_CDS; mRNA.
DR   EMBL; CK545775; -; NOT_ANNOTATED_CDS; mRNA.
DR   EMBL; M76430; AAA27840.1; -; Genomic_DNA.
DR   PIR; A33470; A33470.
DR   RefSeq; NP_001037488.1; NM_001044023.1.
DR   AlphaFoldDB; P21828; -.
DR   STRING; 7091.BGIBMGA009393-TA; -.
DR   iPTMnet; P21828; -.
DR   PRIDE; P21828; -.
DR   EnsemblMetazoa; BGIBMGA009393-RA; BGIBMGA009393-TA; BGIBMGA009393.
DR   GeneID; 693047; -.
DR   KEGG; bmor:693047; -.
DR   CTD; 693047; -.
DR   eggNOG; ENOG502TBZW; Eukaryota.
DR   HOGENOM; CLU_098789_0_0_1; -.
DR   InParanoid; P21828; -.
DR   OMA; LLNEEYC; -.
DR   OrthoDB; 1445259at2759; -.
DR   Proteomes; UP000005204; Unassembled WGS sequence.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   InterPro; IPR008660; L-fibroin.
DR   Pfam; PF05849; L-fibroin; 1.
DR   PIRSF; PIRSF005765; L-fibroin; 1.
PE   1: Evidence at protein level;
KW   Acetylation; Direct protein sequencing; Disulfide bond; Reference proteome;
KW   Secreted; Signal; Silk protein.
FT   SIGNAL          1..16
FT                   /evidence="ECO:0000269|Ref.5"
FT   CHAIN           17..262
FT                   /note="Fibroin light chain"
FT                   /id="PRO_0000021256"
FT   CHAIN           19..262
FT                   /note="Fibroin light chain, short form"
FT                   /id="PRO_0000389559"
FT   MOD_RES         19
FT                   /note="N-acetylserine; in short form"
FT                   /evidence="ECO:0000269|PubMed:2585514"
FT   DISULFID        101..160
FT                   /evidence="ECO:0000255"
FT   DISULFID        190
FT                   /note="Interchain (with C-5244 in heavy chain)"
FT   CONFLICT        46
FT                   /note="A -> R (in Ref. 3; AAA27840)"
FT                   /evidence="ECO:0000305"
SQ   SEQUENCE   262 AA;  27669 MW;  66C68F8BE453B349 CRC64;
     MKPIFLVLLV ATSAYAAPSV TINQYSDNEI PRDIDDGKAS SVISRAWDYV DDTDKSIAIL
     NVQEILKDMA SQGDYASQAS AVAQTAGIIA HLSAGIPGDA CAAANVINSY TDGVRSGNFA
     GFRQSLGPFF GHVGQNLNLI NQLVINPGQL RYSVGPALGC AGGGRIYDFE AAWDAILASS
     DSSFLNEEYC IVKRLYNSRN SQSNNIAAYI TAHLLPPVAQ VFHQSAGSIT DLLRGVGNGN
     DATGLVANAQ RYIAQAASQV HV