What question did this study set out to answer?

To characterize the transient kinetic parameters governing the ATP hydrolysis cycle of mammalian myosin I using a single IQ-domain truncated construct.

July 1, 2000Journal of Biological ChemistryOpen Access

Kinetic Analyses of a Truncated Mammalian Myosin I Suggest a Novel Isomerization Event Preceding Nucleotide Binding

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Population

MI complex

Design

Preclinical

Authors

MGMichael A. GeevesHeart Failure / Cardiomyopathy CPCynthia L. Perreault-MicaleHealthy Start LCLynne M. ColuccioBoston University

Discussion

Member takes

Implication

Remains preclinical without clinical implications; leaves open myosin I equilibrium states as a target for mechanistic cardiovascular studies.

Key Points

To characterize the transient kinetic parameters governing the ATP hydrolysis cycle of mammalian myosin I using a single IQ-domain truncated construct.
Generated MI(1IQ), an 85-kDa catalytic motor domain fragment of rat myr-1 containing the first of six calmodulin-binding IQ domains bound to calmodulin.
Conducted transient kinetic experiments measuring actin affinity, ATP-induced actin-myosin dissociation, and ADP release kinetics in the presence and absence of calcium.
MI(1IQ) bound actin with an affinity of 12 nM, displaying a biphasic ATP-induced dissociation where the fast phase was concentration-dependent and the slow phase was concentration-independent.
ADP inhibited the fast dissociation phase with half-saturation requiring 10 µM ADP in the presence of calcium and 3 µM ADP in the absence of calcium.
The slow phase exhibited the same rate constant as ADP release (8 s⁻¹ with calcium and 3 s⁻¹ without calcium) and persisted despite decreasing ADP concentrations, demonstrating an equilibrium with a nucleotide-inaccessible state.

Structured PICO

Population

MI(1IQ) complex (calmodulin and an epitope-tagged 85-kDa fragment representing the amino-terminal catalytic motor domain and the first of 6 calmodulin-binding IQ domains of the mammalian myosin I gene, rat myr-1)

Intervention

Transient kinetic analysis of the ATP hydrolysis cycle (ATP and ADP addition in the presence and absence of Ca2+)

Outcome

Transient kinetic parameters of the ATP hydrolysis cyclesurrogate

Transient kinetic analyses of a truncated mammalian myosin I suggest a novel isomerization event precedes nucleotide binding, with Ca2+ sensitivity likely mediated by the first IQ domain.

Cite This Study

Geeves et al. (2000) studied this question.

synapsesocial.com/papers/6a71470efebe604dd709f8bd https://doi.org/10.1074/jbc.m000342200

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Implication

Remains preclinical without clinical implications; leaves open myosin I equilibrium states as a target for mechanistic cardiovascular studies.

Kinetic Analyses of a Truncated Mammalian Myosin I Suggest a Novel Isomerization Event Preceding Nucleotide Binding

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Kinetic Analyses of a Truncated Mammalian Myosin I Suggest a Novel Isomerization Event Preceding Nucleotide Binding

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Also Consider

Also Consider