A structural basis for the pH-dependence of cofilin. F-actin interactions.
A marked pH-dependent interaction with F-actin is an important property of typical members of the actin depolymerizing factor (ADF)/cofilin family of abundant actin-binding proteins. ADF/cofilins tend to bind to F-actin with a ratio of 1 : 1 at pH values around 6.5, and to G-actin at pH 8.0. We have investigated the mechanism for the pH-sensitivity. We found no evidence for pH-dependent changes in the structure of cofilin itself, nor for the interaction of cofilin with G-actin. None of the actin-derived, cofilin-binding peptides that we had previously identified [Renoult, C., Ternent, D., Maciver, S.K., Fattoum, A., Astier, C., Benyamin, Y. & Roustan, C. (1999) J. Biol. Chem. 274, 28893-28899] bound cofilin in a pH-sensitive manner. However, we have detected a conformational change in region 75-105 in the actin subdomain 1 by the use of a peptide-directed antibody. A pH-dependent conformational change has also been detected spectroscopically in a similar peptide (84-103) on binding to cofilin. These results are consistent with a model in which pH-dependent motion of subdomain 1 relative to subdomain 2 (through region 75-105) of actin reveals a second cofilin binding site on actin (centered around region 112-125) that allows ADF/cofilin association with the actin filament. This motion requires salt in addition to low pH.
Blondin
Laurence
L
Laboratoire de motilité cellulaire, Université de Montpellier, 2 Place E. Bataillon CC107, 34095 Montpellier Cedex 5, France.
Sapountzi
Vasilia
V
Maciver
Sutherland K
SK
Lagarrigue
Emeline
E
Benyamin
Yves
Y
Roustan
Claude
C
D051339:Actin Depolymerizing Factors; D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D018076:DNA, Complementary; D004735:Energy Transfer; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D018482:Muscle, Skeletal / Q000378:metabolism*; D010957:Plasmids; D011817:Rabbits; D013050:Spectrometry, Fluorescence; D014162:Transfection
D051339:Actin Depolymerizing Factors; D000199:Actins; D018076:DNA, Complementary; D008840:Microfilament Proteins