caa a22 4500 378858963 CHVBK 20180305123341.0 cr unu---uuuuu 161128e20031107xx s 000 0 eng 10.1515/BC.2003.162 doi (NATIONALLICENCE)gruyter-10.1515/BC.2003.162 Thermodynamic Analysis of the Dissociation of the Aldolase Tetramer Substituted at One or Both of the Subunit Interfaces [Elektronische Daten] [D. R. Tolan, B. Schuler, P. T. Beernink, R. Jaenicke] The fructose-1,6-bis(phosphate) aldolase isologous tetramer tightly associates through two different subunit interfaces defined by its 222 symmetry. Both single- and double-interfacial mutant aldolases have a destabilized quaternary structure, but there is little effect on the catalytic activity. These enzymes are however thermolabile. This study demonstrates the temperature-dependent dissociation of the mutant enzymes and determines the dissociation free energies of both mutant and native aldolase. Subunit dissociation is measured by sedimentation equilibrium in the analytical ultracentrifuge. At 25C the tetramerdimer dissociation constants for each single-mutant enzyme are similar, about 10 -6 M. For the double-mutant enzyme, sedimentation velocity experiments on sucrose density gradients support a tetramermonomer equilibrium. Furthermore, sedimentation equilibrium experiments determined a dissociation constant of 10-15 M3 for the double-mutant enzyme. By the same methods the upper limit for the dissociation constant of wild-type aldolase A is approximately 10-28 M3, which indicates an extremely stable tetramer. The thermodynamic values describing monomer-tetramer and dimer-tetramer equilibria are analyzed with regard to possible cooperative interaction between the two subunit interfaces. Copyright © 2003 by Walter de Gruyter GmbH & Co. KG Biochemistry nationallicence Molecular biology nationallicence Cellular biology nationallicence Tolan D. R. aut Schuler B. aut Beernink P. T. aut Jaenicke R. aut Biological Chemistry Walter de Gruyter 384/10-11(2003-11-07), 1463-1471 1431-6730 384:10-11<1463 2003 384 bchm https://doi.org/10.1515/BC.2003.162 text/html Onlinezugriff via DOI 1 research article jats NATIONALLICENCE 856 40 https://doi.org/10.1515/BC.2003.162 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Tolan D. R. aut NATIONALLICENCE 700 1- Schuler B. aut NATIONALLICENCE 700 1- Beernink P. T. aut NATIONALLICENCE 700 1- Jaenicke R. aut NATIONALLICENCE 773 0- Biological Chemistry Walter de Gruyter 384/10-11(2003-11-07), 1463-1471 1431-6730 384:10-11<1463 2003 384 bchm CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-gruyter