Dissociation of ATP-binding cassette nucleotide-binding domain dimers into monomers during the hydrolysis cycle |
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Authors: | Zoghbi Maria E Krishnan Srinivasan Altenberg Guillermo A |
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Affiliation: | Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech Health Sciences Center, Lubbock, Texas 79430-6551, USA. |
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Abstract: | ATP-binding cassette (ABC) proteins have two nucleotide-binding domains (NBDs) that work as dimers to bind and hydrolyze ATP, but the molecular mechanism of nucleotide hydrolysis is controversial. In particular, it is still unresolved whether hydrolysis leads to dissociation of the ATP-induced dimers or opening of the dimers, with the NBDs remaining in contact during the hydrolysis cycle. We studied a prototypical ABC NBD, the Methanococcus jannaschii MJ0796, using spectroscopic techniques. We show that fluorescence from a tryptophan positioned at the dimer interface and luminescence resonance energy transfer between probes reacted with single-cysteine mutants can be used to follow NBD association/dissociation in real time. The intermonomer distances calculated from luminescence resonance energy transfer data indicate that the NBDs separate completely following ATP hydrolysis, instead of opening. The results support ABC protein NBD association/dissociation, as opposed to constant-contact models. |
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Keywords: | ABC Transporter ATP Fluorescence Kinetics Transport LRET MJ0796 Dimerization Luminescence Resonance Energy Transfer |
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