ID   FIBH_BOMMA              Reviewed;         178 AA.
AC   Q99050;
DT   01-DEC-2000, integrated into UniProtKB/Swiss-Prot.
DT   01-DEC-2000, sequence version 2.
DT   25-MAY-2022, entry version 56.
DE   RecName: Full=Fibroin heavy chain;
DE            Short=Fib-H;
DE   AltName: Full=H-fibroin;
DE   Flags: Precursor; Fragment;
GN   Name=FIBH;
OS   Bombyx mandarina (Wild silk moth) (Wild silkworm).
OC   Eukaryota; Metazoa; Ecdysozoa; Arthropoda; Hexapoda; Insecta; Pterygota;
OC   Neoptera; Endopterygota; Lepidoptera; Glossata; Ditrysia; Bombycoidea;
OC   Bombycidae; Bombycinae; Bombyx.
OX   NCBI_TaxID=7092;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RC   TISSUE=Posterior silk gland;
RA   Kusuda J., Tazima Y., Onimaru K., Ninaki O., Suzuki Y.;
RT   "The sequence around the 5' end of the fibroin gene from the wild silkworm,
RT   Bombyx mandarina, and comparison with that of the domesticated species, B.
RT   mori.";
RL   Mol. Gen. Genet. 203:359-364(1986).
CC   -!- FUNCTION: Core component of the silk filament; a strong, insoluble and
CC       chemically inert fiber.
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   -!- TISSUE SPECIFICITY: Produced exclusively in the posterior (PSG) section
CC       of silk glands, which are essentially modified salivary glands.
CC   -!- DOMAIN: Composed of antiparallel beta sheets. The strands of the beta
CC       sheets run parallel to the fiber axis. Long stretches of silk fibroin
CC       are composed of microcrystalline arrays of (-Gly-Ser-Gly-Ala-Gly-Ala-)n
CC       interrupted by regions containing bulkier residues. The fiber is
CC       composed of microcrystalline arrays alternating with amorphous regions.
CC   -!- PTM: The interchain disulfide bridge is essential for the intracellular
CC       transport and secretion of fibroin.
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DR   EMBL; X03973; CAA27612.1; -; Genomic_DNA.
DR   AlphaFoldDB; Q99050; -.
DR   Proteomes; UP000504629; Unplaced.
PE   2: Evidence at transcript level;
KW   Disulfide bond; Reference proteome; Repeat; Signal; Silk protein.
FT   SIGNAL          1..21
FT                   /evidence="ECO:0000255"
FT   CHAIN           22..>178
FT                   /note="Fibroin heavy chain"
FT                   /id="PRO_0000021254"
FT   REGION          149..>178
FT                   /note="Highly repetitive"
FT   CONFLICT        10
FT                   /note="C -> V (in Ref. 1; CAA27612)"
FT                   /evidence="ECO:0000305"
FT   NON_TER         178
SQ   SEQUENCE   178 AA;  18326 MW;  8E15C7E7A9682940 CRC64;
     MRVKTFVILC CALQYVAYTN ANINDFDEDY FGSDVTVQSS NTTDEIIRDA SGAVIEEEIT
     TKKMQRKNKN HGILGKNEKM IKTFVITTDS DGNESIVEED VLMKTLSDGT VAQSYVAADA
     GAYSQSGPYV SNSGYSTHQG YRSDFASAAV GAGAGAGAAA GSGAGAGAGY GAASGAGA