ID   A2M_PACLE               Reviewed;          32 AA.
AC   P20738;
DT   01-FEB-1991, integrated into UniProtKB/Swiss-Prot.
DT   01-FEB-1991, sequence version 1.
DT   25-MAY-2022, entry version 74.
DE   RecName: Full=Alpha-2-macroglobulin homolog;
DE            Short=Alpha-2-M;
DE   Flags: Fragments;
OS   Pacifastacus leniusculus (Signal crayfish).
OC   Eukaryota; Metazoa; Ecdysozoa; Arthropoda; Crustacea; Multicrustacea;
OC   Malacostraca; Eumalacostraca; Eucarida; Decapoda; Pleocyemata; Astacidea;
OC   Astacoidea; Astacidae; Pacifastacus.
OX   NCBI_TaxID=6720;
RN   [1]
RP   PROTEIN SEQUENCE.
RX   PubMed=2476331; DOI=10.1016/0014-5793(89)81019-1;
RA   Hall M., Soederhaell K., Sottrup-Jensen L.;
RT   "Amino acid sequence around the thiolester of alpha 2-macroglobulin from
RT   plasma of the crayfish, Pacifastacus leniusculus.";
RL   FEBS Lett. 254:111-114(1989).
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; A32977; A32977.
DR   PIR; S05404; S05404.
DR   AlphaFoldDB; P20738; -.
DR   MEROPS; I39.007; -.
DR   GO; GO:0005615; C:extracellular space; IEA:InterPro.
DR   GO; GO:0004867; F:serine-type endopeptidase inhibitor activity; IEA:UniProtKB-KW.
DR   InterPro; IPR011626; Alpha-macroglobulin_TED.
DR   InterPro; IPR019742; MacrogloblnA2_CS.
DR   InterPro; IPR008930; Terpenoid_cyclase/PrenylTrfase.
DR   Pfam; PF07678; TED_complement; 1.
DR   SUPFAM; SSF48239; SSF48239; 1.
DR   PROSITE; PS00477; ALPHA_2_MACROGLOBULIN; 1.
PE   1: Evidence at protein level;
KW   Bait region; Direct protein sequencing; Disulfide bond; Protease inhibitor;
KW   Secreted; Serine protease inhibitor; Thioester bond.
FT   CHAIN           1..>32
FT                   /note="Alpha-2-macroglobulin homolog"
FT                   /id="PRO_0000093793"
FT   CROSSLNK        16..19
FT                   /note="Isoglutamyl cysteine thioester (Cys-Gln)"
FT   NON_CONS        11..12
FT                   /evidence="ECO:0000305"
FT   NON_TER         32
SQ   SEQUENCE   32 AA;  3712 MW;  2E62739C5CEB59EB CRC64;
     SYVITTPKMW VMPYGCGEQN MVNFAPNIFI ME