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Localisation of the major reactive lysine residue involved in the selfcrosslinking of proteinase‐activated Limulus α 2 ‐macroglobulin
Author(s) -
Dolmer Klavs,
Husted Lise B.,
Armstrong Peter B.,
Sottrup-Jensen Lars
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(96)00852-6
Subject(s) - limulus , trypsin , chemistry , horseshoe crab , macroglobulin , monomer , covalent bond , biochemistry , lysine , thiol , residue (chemistry) , dimer , amino acid , enzyme , biology , organic chemistry , polymer , paleontology
When α 2 ‐macroglobulin ( α 2 M) from the American horseshoe crab, Limulus polyphemus , reacts with proteinases, its thiol esters, like those of other α‐macroglobulins, become activated, leading to the formation of covalently crosslinked species that can be detected as high molecular weight bands in reducing SDS‐PAGE. While other α‐macroglobulins extensively form crosslinks to the reacting proteinase, Limulus α 2 M does not. It rather becomes internally crosslinked. It was found from N‐terminal sequence analysis of purified [ 14 C]carboxymethylated peptides from Limulus α 2 M‐trypsin complexes that an isopeptide bond formed in approx. 60% yield from the thiol esterified Gln‐1002 specifically to Lys‐254 in the opposing monomer of the disulphide bridged dimer is the main cause of the internal crosslinking.