title: A low affinity ground state conformation for the Dynein microtubule binding domain.
abstract: Dynein interacts with microtubules through a dedicated binding domain that is dynamically controlled to achieve high or low affinity, depending on the state of nucleotide bound in a distant catalytic pocket. The active sites for microtubule binding and ATP hydrolysis communicate via conformational changes transduced through a approximately 10-nm length antiparallel coiled-coil stalk, which connects the binding domain to the roughly 300-kDa motor core. Recently, an x-ray structure of the murine cytoplasmic dynein microtubule binding domain (MTBD) in a weak affinity conformation was published, containing a covalently constrained beta(+) registry for the coiled-coil stalk segment (Carter, A. P., Garbarino, J. E., Wilson-Kubalek, E. M., Shipley, W. E., Cho, C., Milligan, R. A., Vale, R. D., and Gibbons, I. R. (2008) Science 322, 1691-1695). We here present an NMR analysis of the isolated MTBD from Dictyostelium discoideum that demonstrates the coiled-coil beta(+) registry corresponds to the low energy conformation for this functional region of dynein. Addition of sequence encoding roughly half of the coiled-coil stalk proximal to the binding tip results in a decreased affinity of the MTBD for microtubules. In contrast, addition of the complete coiled-coil sequence drives the MTBD to the conformationally unstable, high affinity binding state. These results suggest a thermodynamic coupling between conformational free energy differences in the alpha and beta(+) registries of the coiled-coil stalk that acts as a switch between high and low affinity conformations of the MTBD. A balancing of opposing conformations in the stalk and MTBD enables potentially modest long-range interactions arising from ATP binding in the motor core to induce a relaxation of the MTBD into the stable low affinity state.
authors.affiliation: Division of Translational Medicine, Wadsworth Center, Albany, New York 12201-0509, USA.
authors.forename: Lynn
authors.initials: L
authors.lastname: McNaughton
authors.forename: Irina
authors.initials: I
authors.lastname: Tikhonenko
authors.forename: Nilesh K
authors.initials: NK
authors.lastname: Banavali
authors.forename: David M
authors.initials: DM
authors.lastname: LeMaster
authors.forename: Michael P
authors.initials: MP
authors.lastname: Koonce
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D004023:Dictyostelium / Q000201:enzymology* / Q000235:genetics; D004398:Dyneins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D011485:Protein Binding / Q000502:physiology; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D015800:Protozoan Proteins; D000255:Adenosine Triphosphate; D004398:Dyneins