Kinetic measurements of T----R structural transitions in insulin.
The T6----T3R3 and T3R3----R6-structural transitions of cobalt insulin hexamers as induced by SCN ions or m-cresol were studied in stopped-flow experiments using the absorption in the visible for monitoring their time course. The T6----T3R3 transition induced by either SCN or limited concentrations of m-cresol is mono-exponential with a rate constant of 0.1 s-1 and 0.4 s-1, respectively. A mono-exponential time course is also encountered for the m-cresol-induced T3R3----R6 transition when starting from the T3R3 state preestablished by either SCN or m-cresol. The corresponding rate constants are 1.3 s-1 and 0.49 s-1, respectively. If m-cresol is used beyond the concentration range where transformation is limited to one trimer, two exponentials are required for fitting the time course. The second exponential corresponds to the T3R3----R6 step with a concentration-independent rate constant of 0.4 s-1. The rate constant for the faster T6----T3R3 transition, however, increases with increasing excess of m-cresol.
Karataş
Y
Y
Institut für Biochemie, Rheinisch-Westfälische Technische Hochschule Aachen.
Krüger
P
P
Wollmer
A
A
D000818:Animals; D003035:Cobalt; D003408:Cresols; D007328:Insulin / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation / Q000187:drug effects; D013053:Spectrophotometry; D013329:Structure-Activity Relationship; D013552:Swine; D015032:Zinc
D003408:Cresols; D007328:Insulin; D003035:Cobalt; D015032:Zinc