ID   A2M_OCTVU               Reviewed;          18 AA.
AC   P30800;
DT   01-JUL-1993, integrated into UniProtKB/Swiss-Prot.
DT   01-JUL-1993, sequence version 1.
DT   25-MAY-2022, entry version 68.
DE   RecName: Full=Alpha-2-macroglobulin homolog;
DE            Short=Alpha-2-M;
DE   Flags: Fragment;
OS   Octopus vulgaris (Common octopus).
OC   Eukaryota; Metazoa; Spiralia; Lophotrochozoa; Mollusca; Cephalopoda;
OC   Coleoidea; Octopodiformes; Octopoda; Incirrata; Octopodidae; Octopus.
OX   NCBI_TaxID=6645;
RN   [1]
RP   PROTEIN SEQUENCE.
RX   PubMed=1379044; DOI=10.1042/bj2850521;
RA   Thoegersen I.B., Salvesen G., Brucato F.H., Pizzo S.V., Enghild J.J.;
RT   "Purification and characterization of an alpha-macroglobulin proteinase
RT   inhibitor from the mollusc Octopus vulgaris.";
RL   Biochem. J. 285:521-527(1992).
CC   -!- FUNCTION: Is able to inhibit all four classes of proteinases by a
CC       unique 'trapping' mechanism. This protein has a peptide stretch, called
CC       the 'bait region' which contains specific cleavage sites for different
CC       proteinases. When a proteinase cleaves the bait region, a
CC       conformational change is induced in the protein which traps the
CC       proteinase. The entrapped enzyme remains active against low molecular
CC       weight substrates (activity against high molecular weight substrates is
CC       greatly reduced). Following cleavage in the bait region a thioester
CC       bond is hydrolyzed and mediates the covalent binding of the protein to
CC       the proteinase.
CC   -!- SUBUNIT: Homodimer; disulfide-linked.
CC   -!- SUBCELLULAR LOCATION: Secreted.
CC   -!- SIMILARITY: Belongs to the protease inhibitor I39 (alpha-2-
CC       macroglobulin) family. {ECO:0000305}.
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DR   PIR; S23971; S23971.
DR   AlphaFoldDB; P30800; -.
DR   Proteomes; UP000515154; Genome assembly.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0004867; F:serine-type endopeptidase inhibitor activity; IEA:UniProtKB-KW.
DR   InterPro; IPR019742; MacrogloblnA2_CS.
DR   PROSITE; PS00477; ALPHA_2_MACROGLOBULIN; 1.
PE   1: Evidence at protein level;
KW   Bait region; Direct protein sequencing; Disulfide bond; Protease inhibitor;
KW   Reference proteome; Secreted; Serine protease inhibitor; Thioester bond.
FT   CHAIN           <1..>18
FT                   /note="Alpha-2-macroglobulin homolog"
FT                   /id="PRO_0000093792"
FT   CROSSLNK        5..8
FT                   /note="Isoglutamyl cysteine thioester (Cys-Gln)"
FT   NON_TER         1
FT   NON_TER         18
SQ   SEQUENCE   18 AA;  2011 MW;  D8D61C473D901C9D CRC64;
     KPSGCGEQNM INFYPNVL