TY - JOUR
T1 - Visual insight into how low pH alone can induce actin-severing ability in gelsolin under calcium-free conditions
AU - Garg, Renu
AU - Peddada, Nagesh
AU - Sagar, Amin
AU - Nihalani, Deepak
AU - Ashish,
PY - 2011/6/10
Y1 - 2011/6/10
N2 - Gelsolin is a key actin cytoskeleton-modulating protein primarily regulated by calcium and phosphoinositides. In addition, low pH has also been suggested to activate gelsolin in the absence of Ca2+ ions, although no structural insight on this pathway is available except for a reported decrement in its diffusion coefficient at low pH. We also observed ∼1.6-fold decrease in the molecular mobility of recombinant gelsolin when buffer pH was lowered from 9 to 5. Analysis of the small angle x-ray scattering data collected over the same pH range indicated that the radius of gyration and maximum linear dimension of gelsolin molecules increased from 30.3 to 34.1 Å and from 100 to 125 Å, respectively. Models generated for each dataset indicated that similar to the Ca2+-induced process, low pHalso promotes unwinding of this six-domain protein but only partially. It appeared that pH is able to induce extension of the G1 domain from the rest of the five domains, whereas the Ca2+-sensitive latch between G2 and G6 domains remains closed. Interestingly, increasing the free Ca2+ level to merely ∼40 nM, the partially open pH 5 shape "sprung open" to a shape seen earlier for this protein at pH 8 and 1 mM free Ca2+. Also, pH alone could induce a shape where the g3-g4 linker of gelsolin was open when we truncated the C-tail latch from this protein. Our results provide insight into how under physiological conditions, a drop in pH can fully activate the F-actin-severing shape of gelsolin with micromolar levels of Ca2+ available.
AB - Gelsolin is a key actin cytoskeleton-modulating protein primarily regulated by calcium and phosphoinositides. In addition, low pH has also been suggested to activate gelsolin in the absence of Ca2+ ions, although no structural insight on this pathway is available except for a reported decrement in its diffusion coefficient at low pH. We also observed ∼1.6-fold decrease in the molecular mobility of recombinant gelsolin when buffer pH was lowered from 9 to 5. Analysis of the small angle x-ray scattering data collected over the same pH range indicated that the radius of gyration and maximum linear dimension of gelsolin molecules increased from 30.3 to 34.1 Å and from 100 to 125 Å, respectively. Models generated for each dataset indicated that similar to the Ca2+-induced process, low pHalso promotes unwinding of this six-domain protein but only partially. It appeared that pH is able to induce extension of the G1 domain from the rest of the five domains, whereas the Ca2+-sensitive latch between G2 and G6 domains remains closed. Interestingly, increasing the free Ca2+ level to merely ∼40 nM, the partially open pH 5 shape "sprung open" to a shape seen earlier for this protein at pH 8 and 1 mM free Ca2+. Also, pH alone could induce a shape where the g3-g4 linker of gelsolin was open when we truncated the C-tail latch from this protein. Our results provide insight into how under physiological conditions, a drop in pH can fully activate the F-actin-severing shape of gelsolin with micromolar levels of Ca2+ available.
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U2 - 10.1074/jbc.M111.236943
DO - 10.1074/jbc.M111.236943
M3 - Article
C2 - 21498516
AN - SCOPUS:79957995746
SN - 0021-9258
VL - 286
SP - 20387
EP - 20397
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 23
ER -