Ca-dependent binding of actin to gelsolin.
Ca(2+) of 0.3-1.0 microM induces both the exposure of tryptic cleavage sites within the gelsolin molecule inaccessible in the Ca-free conformation, and binding of one actin monomer to the N-terminal half of gelsolin. On the other hand, gelsolin-induced enhancement of pyrene actin fluorescence was observed only above 50 microM Ca(2+), and a ternary actin/gelsolin complex preformed in 200 microM Ca(2+) was stable only above 30 microM Ca(2+). These results provide direct evidence for Ca-induced transitions from closed to open conformation of the gelsolin molecule in the range of 3 x 10(-7) to 10(-6) M Ca(2+). They also suggest that Ca(2+)>10(-5) M is required to stabilize actin-actin contacts in the 2:1 actin/gelsolin complex.
Khaitlina
Sofia
S
Institute of Cytology RAS, St. Petersburg, Russia.
Hinssen
Horst
H
D000199:Actins / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D018260:Gelsolin / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011721:Pyrenes; D013552:Swine
D000199:Actins; D018260:Gelsolin; D011721:Pyrenes; C030984:pyrene; D002118:Calcium