Changes in structure of alpha 2-macroglobulin upon reaction with trypsin as assessed by light scattering and differential scanning calorimetry.
Employing a combination of static and dynamic light scattering, as well as differential scanning calorimetry (DSC), the structural changes which appear in alpha 2-macroglobulin (alpha 2M) upon trypsin binding have been further characterized. Light-scattering measurements suggest that a 15% reduction in both the hydrodynamic radius and radius of gyration occurs when two molecules of trypsin complex to alpha 2M. Approx. 85% of this trypsin-induced compaction results from the binding of the first proteinase. A complementary result was obtained from DSC measurements in which the major fraction of the trypsin-induced conversion of alpha 2M to a single more thermally stable form results from interaction with the first proteinase molecule. These observations support a functionally asymmetric model of trypsin binding to alpha 2M in which the significant reduction in size of the complex is primarily due to the initial interaction of alpha 2M with a single proteinase molecule.
Middaugh
C R
CR
Merck Research Laboratories, West Point, PA 19486.
Steadman
B L
BL
Schurtenberger
P
P
Lee
D C
DC
Chlebowski
J F
JF
D002152:Calorimetry, Differential Scanning; D006801:Humans; D008027:Light; D011487:Protein Conformation; D012542:Scattering, Radiation; D014357:Trypsin / Q000378:metabolism*; D000511:alpha-Macroglobulins / Q000737:chemistry* / Q000378:metabolism
D000511:alpha-Macroglobulins; D014357:Trypsin