Identification of a polyphosphoinositide-binding sequence in an actin monomer-binding domain of gelsolin.
Gelsolin is an actin filament-severing and -capping protein that has profound effects on actin filament organization and assembly. It is activated by Ca2+ and inhibited by polyphosphoinositides (PPI). We have previously shown that PPI inhibit actin filament severing by the amino-terminal half of gelsolin and hypothesized that this is mediated through inhibition of actin filament side binding (by domains II-III of gelsolin), a requisite first step in severing. In this paper, we report that the subsequent step in severing, which is mediated by an actin monomer binding site located in domain I of gelsolin, is also regulated by PPI. We used deletional mutagenesis and a synthetic peptide to locate the sequence required for high affinity PPI binding in domain I. Our results show that the PPI-binding sequence has a basic charge distribution that is also present in the PPI-regulated actin filament side binding domain, and the two gelsolin PPI-binding sites have similar PPI-binding affinities. In addition, a similar motif is present in several other PPI-binding proteins, including a highly conserved region in the phospholipase C family. We propose that the sequences identified in gelsolin may represent a consensus for PPI binding in a variety of proteins.
Yu
F X
FX
Department of Physiology, University of Texas Southwestern Medical Center, Dallas 75235.
Sun
H Q
HQ
Janmey
P A
PA
Yin
H L
HL
D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D002850:Chromatography, Gel; D002942:Circular Dichroism; D004247:DNA; D004591:Electrophoresis, Polyacrylamide Gel; D018260:Gelsolin; D006801:Humans; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols / Q000378:metabolism*
D000199:Actins; D002135:Calcium-Binding Proteins; D018260:Gelsolin; D008840:Microfilament Proteins; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D004247:DNA