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Thiol ester role in correct folding and conformation of human α 2 ‐macroglobulin
Author(s) -
Gettins Peter G.W.,
Boel Esper,
Crews Brenda C.
Publication year - 1994
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(94)80430-3
Subject(s) - macroglobulin , thiol , folding (dsp implementation) , chemistry , biochemistry , engineering , electrical engineering
To determine the role of the thiol ester in the folding of human α 2 ‐macroglobulin (α 2 M) in the active conformation, we have characterized a recombinant variant of α 2 M, C949S, expressed in baby hamster kidney cells, that lacks the thiol ester‐forming cysteine. C949S α 2 M behaves like methylamine‐treated plasma α 2 M, with correctly formed inter‐subunit disulfide bridges, non‐covalent association of covalent dimers to form tetramers, and exposure of the receptor binding domain, but an inability to inhibit proteinases, and inaccessibility of the bait regions to proteolysis. We concluded that correct folding of monomers or their association to give tetrameric α 2 M does not require a pre‐formed thiol ester. Active α 2 M may form in vivo by a two‐step process involving initial folding to give a structure resembling that of C949S α 2 M followed by thiol ester formation and a conformational change that gives the native active state.