Ligand binding to wild-type and E-B13Q mutant insulins: a three-state allosteric model system showing half-site reactivity.
By using ultra-violet and visible absorbance in conjunction with high field 1H-nuclear magnetic resonance spectroscopy, the insulin hexamer has been shown to undergo two allosteric transitions in solution involving three allosteric states (T6<-->T3 R3<-->R6). A simple mathematical model consisting of four variables has been derived that quantitatively describes the complex homotropic and heterotropic interactions that modulate these allosteric transitions. The mutation of one residue, Glu-B13 to Gln, results in an unexpected change in the T3R3 to R6 equilibrium by a factor of 10(7).
Bloom
C R
CR
Department of Biochemistry, University of California, Riverside 92521.
Choi
W E
WE
Brzovic
P S
PS
Ha
J J
JJ
Huang
S T
ST
Kaarsholm
N C
NC
Dunn
M F
MF
D000495:Allosteric Site; D018698:Glutamic Acid / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D007328:Insulin / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D009154:Mutation; D013056:Spectrophotometry, Ultraviolet
D007328:Insulin; D008024:Ligands; D005973:Glutamine; D018698:Glutamic Acid