Spontaneous subunit exchange in porcine liver fructose-1,6-bisphosphatase.
No evidence to date suggests the possibility of subunit exchange between tetramers of mammalian fructose-1,6-bisphosphatase. An engineered fructose-1,6-bisphosphatase, with subunits of altered electrostatic charge, exhibits spontaneous subunit exchange with wild-type enzyme in the absence of ligands. The exchange process reaches equilibrium in approximately 5 h at 4 degrees C, as monitored by non-denaturing gel electrophoresis and anion exchange chromatography. Active site ligands, such as fructose 6-phosphate, abolish subunit exchange at the level of the monomer, but permit dimer-dimer exchanges. AMP, alone or in the presence of active site ligands, abolishes all exchange processes. Exchange phenomena may play a role in the kinetic mechanism of allosteric regulation of fructose-1,6-bisphosphatase.
Department of Biochemistry, Biophysics, and Molecular Biology, 1210 Molecular Biology Bldg., Iowa State University, Ames, IA 50011, USA.
S W
SW
Nelson
R B
RB
Honzatko
H J
HJ
Fromm
D000249:Adenosine Monophosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D006597:Fructose-Bisphosphatase / Q000737:chemistry*; D008099:Liver / Q000737:chemistry / Q000201:enzymology*; D011487:Protein Conformation; D021122:Protein Subunits; D013552:Swine
D021122:Protein Subunits; D000249:Adenosine Monophosphate; D006597:Fructose-Bisphosphatase