Polymerization kinetics of ADP- and ADP-Pi-actin determined by fluorescence microscopy

@article{citeulike:1324508, abstract = {We used fluorescence microscopy to determine how polymerization of Mg-ADP-actin depends on the concentration of phosphate. From the dependence of the elongation rate on the actin concentration and direct observations of depolymerizing filaments, we measured the polymerization rate constants of ADP-actin and ADP-Pi-actin. Saturating phosphate reduces the critical concentration for polymerization of Mg-ADP-actin from 1.8 to 0.06 {micro}M almost entirely by reducing the dissociation rate constants at both ends. Saturating phosphate increases the barbed end association rate constant of Mg-ADP-actin 15\%, but this value is still threefold less than that of ATP-actin. Thus, ATP hydrolysis without phosphate dissociation must change the conformation of polymerized actin. Analysis of depolymerization experiments in the presence of phosphate suggests that phosphate dissociation near the terminal subunits is much faster than in the interior. Remarkably, 10 times more phosphate is required to slow the depolymerization of the pointed end than the barbed end, suggesting a weak affinity of phosphate near the pointed end. Our observations of single actin filaments provide clues about the origins of the difference in the critical concentration at the two ends of actin filaments in the presence of ATP. 10.1073/pnas.0702510104}, author = {Fujiwara, Ikuko and Vavylonis, Dimitrios and Pollard, Thomas D. }, citeulike-article-id = {1324508}, doi = {10.1073/pnas.0702510104}, journal = {PNAS}, keywords = {actin, experiment, polymerization, protein}, month = {May}, number = {21}, pages = {8827--8832}, posted-at = {2007-05-24 08:36:34}, priority = {2}, title = {Polymerization kinetics of ADP- and ADP-Pi-actin determined by fluorescence microscopy}, url = {http://dx.doi.org/10.1073/pnas.0702510104}, volume = {104}, year = {2007} }

TY - JOUR ID - citeulike:1324508 L3 - citeulike-article-id:1324508 TI - Polymerization kinetics of ADP- and ADP-Pi-actin determined by fluorescence microscopy JF - PNAS VL - 104 IS - 21 SP - 8827 EP - 8832 N2 - We used fluorescence microscopy to determine how polymerization of Mg-ADP-actin depends on the concentration of phosphate. From the dependence of the elongation rate on the actin concentration and direct observations of depolymerizing filaments, we measured the polymerization rate constants of ADP-actin and ADP-Pi-actin. Saturating phosphate reduces the critical concentration for polymerization of Mg-ADP-actin from 1.8 to 0.06 {micro}M almost entirely by reducing the dissociation rate constants at both ends. Saturating phosphate increases the barbed end association rate constant of Mg-ADP-actin 15%, but this value is still threefold less than that of ATP-actin. Thus, ATP hydrolysis without phosphate dissociation must change the conformation of polymerized actin. Analysis of depolymerization experiments in the presence of phosphate suggests that phosphate dissociation near the terminal subunits is much faster than in the interior. Remarkably, 10 times more phosphate is required to slow the depolymerization of the pointed end than the barbed end, suggesting a weak affinity of phosphate near the pointed end. Our observations of single actin filaments provide clues about the origins of the difference in the critical concentration at the two ends of actin filaments in the presence of ATP. 10.1073/pnas.0702510104 KW - actin KW - experiment KW - polymerization KW - protein AU - Fujiwara, Ikuko AU - Vavylonis, Dimitrios AU - Pollard, Thomas PY - 2007/05/22/ UR - http://dx.doi.org/10.1073/pnas.0702510104 ER -