Control of the assembly of ATP- and ADP-actin by formins and profilin.
Formin proteins nucleate actin filaments, remaining processively associated with the fast-growing barbed ends. Although formins possess common features, the diversity of functions and biochemical activities raised the possibility that formins differ in fundamental ways. Further, a recent study suggested that profilin and ATP hydrolysis are both required for processive elongation mediated by the formin mDia1. We used total internal reflection fluorescence microscopy to observe directly individual actin filament polymerization in the presence of two mammalian formins (mDia1 and mDia2) and two yeast formins (Bni1p and Cdc12p). We show that these diverse formins have the same basic properties: movement is processive in the absence or presence of profilin; profilin accelerates elongation; and actin ATP hydrolysis is not required for processivity. These results suggest that diverse formins are mechanistically similar, but the rates of particular assembly steps vary.
Kovar
David R
DR
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA.
Harris
Elizabeth S
ES
Mahaffy
Rachel
R
Higgs
Henry N
HN
Pollard
Thomas D
TD
D000199:Actins / Q000096:biosynthesis*; D000244:Adenosine Diphosphate / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D000080865:Formins; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins; D008954:Models, Biological; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D051304:Profilins / Q000502:physiology*
D000199:Actins; D002352:Carrier Proteins; C491464:Diap1 protein, mouse; D000080865:Formins; D008869:Microtubule-Associated Proteins; D051304:Profilins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; C508552:Dia2 protein, mouse; D009252:NADPH Dehydrogenase