title: Electron microscope studies of human alpha 2-macroglobulin-chymotrypsin complex: demonstration that the two structures assigned to native and proteolyzed alpha 2-macroglobulin represent two views of the proteolyzed molecule.
abstract: Electron microscope studies of native and protease-bound human alpha 2-macroglobulin have led to two contradictory models for these two structures. One viewpoint maintains that the native structure has the shape of )+(, which contracts on binding of the protease to the shape of ([). An opposing view proposes that the native structure has the shape of a padlock and that )+( and ([) are the side and end views of the proteolyzed molecule. In this investigation, electron microscope studies of the alpha-chymotrypsin-treated alpha 2-macroglobulin utilizing a tilt stage have shown that the two shapes [)+( and ([)] interconvert. This demonstrates that these two shapes represent the side and end views of the proteolyzed alpha 2-macroglobulin which are related by a 90 degree rotation of the prototype molecule.
authors: Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030.
authors: J K
authors: JK
authors: Stoops
authors: J P
authors: JP
authors: Bretaudiere
authors: D K
authors: DK
authors: Strickland
mesh_terms: D002918:Chymotrypsin / Q000097:blood*; D006801:Humans; D006868:Hydrolysis; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D013329:Structure-Activity Relationship; D000511:alpha-Macroglobulins / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D046911:Macromolecular Substances; D000511:alpha-Macroglobulins; D002918:Chymotrypsin