The carboxy-terminal tail domain of vinculin contains a cryptic binding site for acidic phospholipids.
Using a gel filtration assay, we have characterized the binding of acidic phospholipids to vinculin. Vinculin binds phosphatidyinositol (Kd approximately 5 microM) in a reversible, saturable manner in low ionic strength buffers. This interaction is inhibited substantially at 100 mM NaCl and therefore may not be of physiological interest. In contrast, the carboxy-terminal 30-kDa fragment of vinculin, produced by S. aureus V8 protease cleavage, binds acidic phospholipids more tightly than the intact protein, and in a manner insensitive to 100 mM NaCl. Re-addition of the 95-kDa head fragment to the tail restores salt-sensitivity to the tail-lipid interaction. These data indicate that under physiologic ionic conditions, the intramolecular head-tail interaction in vinculin masks a high affinity acidic phospholipid binding site present in the tail domain.
Johnson
R P
RP
Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Craig
S W
SW
D000818:Animals; D001665:Binding Sites; D002645:Chickens; D002850:Chromatography, Gel; D066298:In Vitro Techniques; D009994:Osmolar Concentration; D010446:Peptide Fragments / Q000378:metabolism; D010712:Phosphatidic Acids / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D010718:Phosphatidylserines / Q000378:metabolism*; D016596:Vinculin / Q000737:chemistry / Q000378:metabolism*
D010446:Peptide Fragments; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D010716:Phosphatidylinositols; D010718:Phosphatidylserines; D016596:Vinculin