Image processing of electron micrographs of human alpha 2-macroglobulin half-molecules induced by Cd2+.
Human alpha 2-macroglobulin is a tetrameric plasma inhibitor of proteinases. Its dissociation by Cd2+ gives functional dimers. Electron microscopy of negatively stained dimers shows their round-ended cylindrical shape with furrows delimiting 3 main stain-excluding domains. Image processing of electron micrographs shows the existence of 2 main orientations of the dimers on the carbon support film. The dimer is composed of 2 curved monomers linked in a central domain, and related by a 90 degree rotation. Taking into account the known primary structure of alpha 2-macroglobulin and the linkage of the 2 constitutive monomers by 2 disulfide bonds, the molecular organization of the dimer is discussed, extended to the tetrameric molecule and compared to the published models of human alpha 2-macroglobulin.
Thomas
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D
Laboratoire de Biologie Cellulaire, UA 256 CNRS; Université de Rennes, France.
Flifla
M J
MJ
Escoffier
B
B
Barray
M
M
Delain
E
E
D002104:Cadmium / Q000494:pharmacology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008854:Microscopy, Electron / Q000379:methods; D015394:Molecular Structure; D000511:alpha-Macroglobulins / Q000032:analysis* / Q000378:metabolism
D000511:alpha-Macroglobulins; D002104:Cadmium