TY - JOUR
T1 - Identification of a polyphosphoinositide-modulated domain in gelsolin which binds to the sides of actin filaments
AU - Yin, H. L.
AU - Iida, K.
AU - Janmey, P. A.
PY - 1988
Y1 - 1988
N2 - Gelsolin is a Ca2+- and polyphosphoinositide-modulated actin-binding protein which severs actin filaments, nucleates actin assembly, and caps the 'barbed' end of actin filaments. Proteolytic cleavage analysis of human plasma gelsolin has shown that the NH2-terminal half of the molecule severs actin filaments almost as effectively as native gelsolin in a Ca2+-insensitive but polyphosphoinositide-inhibited manner. Furhter proteolysis of the NH2-terminal half generates two unique fragments (CT14N and CT28N), which have minimal severing activity. Under physiological salt conditions, CT14N binds monomeric actin coupled to Sepharose but CT28N does not. In this paper, we show that CT28N binds stoichiometrically and with high affinity to actin subunits in filaments, suggesting that it preferentially recognizes the conformation of polymerized actin. Analyasis of the binding data shows that actin filaments have one class of CT28N binding sites with K(d) = 2.0 x 10-7 M, which saturates at a CT28N/actin subunit ratio of 0.8. Binding of CT28N to actin filaments is inhibited by phosphatidylinositol 4,5-bisphosphate micelles. In contrast, neither CT14N nor another actin-binding domain located in the COOH-terminal half of gelsolin form stable stoichiometric complexes with actin along the filaments, and their binding to actin monomers is not inhibited by PIP2. Based on these observations, we propose that CT28N is the polyphosphoinositide-regulated actin-binding domain which allows gelsolin to bind to actin subunits within a filament before severing.
AB - Gelsolin is a Ca2+- and polyphosphoinositide-modulated actin-binding protein which severs actin filaments, nucleates actin assembly, and caps the 'barbed' end of actin filaments. Proteolytic cleavage analysis of human plasma gelsolin has shown that the NH2-terminal half of the molecule severs actin filaments almost as effectively as native gelsolin in a Ca2+-insensitive but polyphosphoinositide-inhibited manner. Furhter proteolysis of the NH2-terminal half generates two unique fragments (CT14N and CT28N), which have minimal severing activity. Under physiological salt conditions, CT14N binds monomeric actin coupled to Sepharose but CT28N does not. In this paper, we show that CT28N binds stoichiometrically and with high affinity to actin subunits in filaments, suggesting that it preferentially recognizes the conformation of polymerized actin. Analyasis of the binding data shows that actin filaments have one class of CT28N binding sites with K(d) = 2.0 x 10-7 M, which saturates at a CT28N/actin subunit ratio of 0.8. Binding of CT28N to actin filaments is inhibited by phosphatidylinositol 4,5-bisphosphate micelles. In contrast, neither CT14N nor another actin-binding domain located in the COOH-terminal half of gelsolin form stable stoichiometric complexes with actin along the filaments, and their binding to actin monomers is not inhibited by PIP2. Based on these observations, we propose that CT28N is the polyphosphoinositide-regulated actin-binding domain which allows gelsolin to bind to actin subunits within a filament before severing.
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U2 - 10.1083/jcb.106.3.805
DO - 10.1083/jcb.106.3.805
M3 - Article
C2 - 2831234
AN - SCOPUS:0023849688
SN - 0021-9525
VL - 106
SP - 805
EP - 812
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 3
ER -