Disruption of the aldolase A tetramer into catalytically active monomers.

AUTOR(ES)

Beernink, P T

RESUMO

The fructose-1,6-bisphosphate aldolase (EC 4.1.2.13) homotetramer has been destabilized by site-directed mutagenesis at the two different subunit interfaces. A double mutant aldolase, Q125D/E224A, sediments as two distinct species, characteristic of a slow equilibrium, with velocities expected for the monomer and tetramer. The aldolase monomer is shown to be catalytically active following isolation from sucrose density gradients. The isolated aldolase monomer had 72% of the specific activity of the wild-type enzyme and a slightly lower Michaelis constant, clearly indicating that the quaternary structure is not required for catalysis. Cross-linking of the isolated monomer confirmed that it does not rapidly reequilibrate with the tetramer following isolation. There was a substantial difference between the tetramer and monomer in their inactivation by urea. The stability toward both urea and thermal inactivation of these oligomeric variants suggests a role for the quaternary structure in maintaining the stability of aldolase, which may be an important role of quaternary structure in many proteins.

Documentos Relacionados

• SecYEG assembles into a tetramer to form the active protein translocation channel
• Two-hybrid system as a model to study the interaction of beta-amyloid peptide monomers.
• Concerted folding of a Candida ribozyme into the catalytically active structure posterior to a rapid RNA compaction
• Enzymatic and NMR analysis of oligoribonucleotides synthesized with 2'-tert-butyldimethylsilyl protected cyanoethylphosphoramidite monomers.
• Identification of the cysteine residues involved in the class I disulfide bonds of the human insulin receptor: properties of insulin receptor monomers.