| 11498081 |
Jensen PE, Gunnarsson M, Stigbrand T: Conformational state and receptor recognition of the C-terminal domain of human alpha (2)-macroglobulin after dissociation into half-molecules. Clin Chim Acta. 2001 Aug 20;310(2):157-63.
BACKGROUND: Dissociation of native human alpha (2)-macroglobulin (alpha (2) M) by sodium thiocyanate generates stable half-molecules with intact thiol esters. Significant conformational changes occur by the dissociation, which are similar to those occurring by transformation from native to methylamine-treated alpha (2)-macroglobulin. METHODS: The conformational state of the receptor-binding domain of the half-molecules was investigated by receptor binding and clearance studies, and by use of a panel of 11 monoclonal antibodies (mAbs) specific for the 18-kDa C-terminal receptor-binding fragment of alpha (2)-macroglobulin. RESULTS: The half-molecules simultaneously express epitopes specific for native, as well as epitopes specific for transformed alpha (2)-macroglobulin. While it is possible to immunochemically discriminate between the different forms of tetrameric protein, the half-molecules retain a conformational state with no observed conformational changes in the C-terminal domain following cleavage of thiol esters or bait regions. The in vivo clearance rate in mice was consequently significantly slower for the half-molecules than for the tetrameric receptor-recognized forms of alpha (2)-macroglobulin. Furthermore, half-molecules demonstrate lower affinity for binding to mouse macrophages than methylamine-treated tetrameric alpha (2)-macroglobulin in competition studies. CONCLUSIONS: It is suggested that contact zones are functionally important for mediating conformational switches, which result in trapping and exposure of the receptor-binding sites. |
12(0,0,1,7) |