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The kinetics of conformational changes of α 2 ‐macroglobulin determined by time resolved X‐ray solution scattering
Author(s) -
Arakawa Hideo,
Urisaka Takuji,
Tsuruta Hirotsugu,
Amemiya Yoshiyuki,
Kihara Hiroshi,
Ikaia Atsushi
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)80267-x
Subject(s) - radius of gyration , chemistry , reaction rate constant , conformational change , kinetics , macroglobulin , alpha 2 macroglobulin , gyration , chymotrypsin , crystallography , trypsin , enzyme , stereochemistry , polymer , organic chemistry , biochemistry , physics , geometry , mathematics , quantum mechanics
The rate of gross conformational change of α 2 ‐macroglobulin (α 2 M) during its proteinase trapping was directly determined for the first time using time‐resolved X‐ray solution scattering. Decrease of radius of gyration was observed under pseudo‐first‐order conditions with excess proteinases, which exhibited a monophasic timecourse. The rate constants were 0.5 ± 0.1 s −1 and 0.8 ± 0.2 s −1 for the reaction with chymotrypsin and trypsin, respectively. There was no concentration dependence of the observed rate constants. Therefore, the rate‐limiting step of the gross conformational change was not the bimolecular encounter reaction between α 2 M and proteinases, which requires a new proposal of pre‐trapping of proteinases before the gross conformational change.