Actophorin preferentially binds monomeric ADP-actin over ATP-bound actin: consequences for cell locomotion.
Actophorin from Acanthamoeba castellanii severs actin filaments and sequesters actin monomers. Here we report that actophorin binds ADP-bound monomers with higher affinity than ATP-bound monomers. Actophorin is therefore much less efficient at severing actin filaments in the presence of ADP compared to ATP, particularly taking account of the higher critical concentration in ADP. Monomer binding is also reduced in the presence of 25 mM inorganic phosphate (which is assumed to form ADP.Pi-actin). These findings are discussed in the light of observations on the nucleotide specificity of other monomer binding proteins and related to the role of actin in lamellar protrusion and cell locomotion.
MRC Laboratory of Molecular Biology, Cambridge, UK.
S K
SK
Maciver
A G
AG
Weeds
D000199:Actins / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology*; D002850:Chromatography, Gel; D018076:DNA, Complementary / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D005822:Genetic Vectors; D007700:Kinetics; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D014783:Viscosity
C042634:ADP-G-actin; C022920:ATP-G-actin; D000199:Actins; D018076:DNA, Complementary; D008840:Microfilament Proteins; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C047604:actophorin protein, Acanthamoeba; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate