Severing of F-actin by yeast cofilin is pH-independent.
Cofilin plays an important role in actin turnover in cells by severing actin filaments and accelerating their depolymerization. The role of pH in the severing by cofilin was examined using fluorescence microscopy. To facilitate the imaging of actin filaments and to avoid the use of rhodamine phalloidin, which competes with cofilin, alpha-actin was labeled with tetramethylrhodamine cadaverine (TRC) at Gln41. The TRC-labeling inhibited actin treadmilling strongly, as measured by epsilonATP release. Cofilin binding, detected via an increase in light scattering, and the subsequent conformational change in filament structure, as detected by TRC fluorescence decay, occurred 2-3 times faster at pH 6.8 than at pH 8.0. In contrast, actin filaments severing by cofilin was pH-independent. The pH-independent severing by cofilin was confirmed using actin labeled at Cys374 with Oregon Green 488 maleimide. The depolymerization of actin by cofilin was faster at high pH.
Pavlov
Dmitry
D
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA.
Muhlrad
Andras
A
Cooper
John
J
Wear
Martin
M
Reisler
Emil
E
D008841:Actin Cytoskeleton / Q000378:metabolism; D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002264:Carboxylic Acids / Q000737:chemistry; D004985:Ethenoadenosine Triphosphate / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D051379:Mice; D011485:Protein Binding; D011817:Rabbits; D012235:Rhodamines / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D013997:Time Factors
D051339:Actin Depolymerizing Factors; D000199:Actins; D002264:Carboxylic Acids; D004985:Ethenoadenosine Triphosphate; C436864:Oregon Green 488 carboxylic acid; D012235:Rhodamines; C005358:tetramethylrhodamine