Correlation between self-association modes and GTPase activation of dynamin.
The GTPase activity of dynamin is obligatorily coupled, by a mechanism yet unknown, to the internalization of clathrin-coated endocytic vesicles. Dynamin oligomerizes in vitro and in vivo and both its mechanical and enzymatic activities appear to be mediated by this self-assembly. In this study we demonstrate that dynamin is characterized by a tetramer/monomer equilibrium with an equilibrium constant of 1.67 x 10(17) M(-3). Stopped-flow fluorescence experiments show that the association rate constant for 2'(3')-O-N-methylanthraniloyl (mant)GTP is 7.0 x 10(-5) M(-1) s(-1) and the dissociation rate constant is 2.1 s(-1), whereas the dissociation rate constant for mantdeoxyGDP is 93 s(-1). We also demonstrate the cooperativity of dynamin binding and GTPase activation on a microtubule lattice. Our results indicate that dynamin self-association is not a sufficient condition for the expression of maximal GTPase activity, which suggests that dynamin molecules must be in the proper conformation or orientation if they are to form an active oligomer.
Binns
D D
DD
Department of Pharmacology, U.T. Southwestern Medical Center, Dallas, Texas 75235-9041, USA.
Barylko
B
B
Grichine
N
N
Atkinson
M A
MA
Helms
M K
MK
Jameson
D M
DM
Eccleston
J F
JF
Albanesi
J P
JP
D000818:Animals; D001921:Brain / Q000201:enzymology; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D034281:Dynamins; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D007700:Kinetics; D008870:Microtubules / Q000378:metabolism; D008954:Models, Biological; D012965:Sodium Chloride / Q000494:pharmacology; D013997:Time Factors; D014404:Tubulin / Q000378:metabolism; D014461:Ultracentrifugation
D014404:Tubulin; D012965:Sodium Chloride; D020558:GTP Phosphohydrolases; D034281:Dynamins