A Kinetic Analysis of the Nucleotide-induced Allosteric Transitions in a Single-ring Mutant of GroEL

The function of GroE requires a complex system of allosteric communication driven by protein–nucleotide interactions. These rearrangements couple the binding and hydrolysis of ATP to an overall reaction cycle in which substrate proteins are bound, encapsulated and released. Positive cooperativity wi...

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Bibliographic Details
Published in:Journal of molecular biology 2004-05, Vol.338 (5), p.969-977
Main Authors: Poso, Daniel, Clarke, Anthony R., Burston, Steven G.
Format: Article
Language:English
Subjects:
Adenosine Diphosphate - metabolism
Adenosine Triphosphate - metabolism
Allosteric Regulation
ATP
Chaperonin 60 - genetics
Chaperonin 60 - metabolism
chaperonins
Chaperonins - genetics
Chaperonins - metabolism
GroEL
GroES
Kinetics
Mutation
Nucleotides - metabolism
Protein Binding
Protein Conformation
SR1
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Summary:The function of GroE requires a complex system of allosteric communication driven by protein–nucleotide interactions. These rearrangements couple the binding and hydrolysis of ATP to an overall reaction cycle in which substrate proteins are bound, encapsulated and released. Positive cooperativity with respect to ATP binding occurs within one heptameric ring of GroEL, while negative cooperativity between the two rings generates an inherent asymmetry between the two rings. A previously engineered mutant of GroEL in which the ring–ring contacts are broken gives rise to a single-ring version of the wild-type chaperonin (SR1). We have studied the kinetics of the nucleotide-induced conformational changes in a single-tryptophan variant of SR1 (Y485W-SR1) and compared the resulting data with those we reported previously for the double-ring, single-tryptophan variant of wild-type GroEL (Y485W-GroEL). Remarkably, the parting of the rings does not have a major effect on the conformational changes occurring within the heptameric ring and a kinetic model is presented to describe the sequence of structural rearrangements that occur upon ATP binding to the SR1 molecule. The observation that both the ATP-induced and ADP-induced conformational rearrangements occur more rapidly in the SR1 than they do in wild-type GroEL, indicates that intra-ring conformational changes in the double-ring structure must overcome conformational constraints provided by the presence of the second ring. Lastly, the data presented here imply a role for inter-ring allostery in controlling the dissociation–association behaviour of the GroES co-protein in the overall reaction cycle.
ISSN:0022-2836
1089-8638
DOI:10.1016/j.jmb.2004.03.010