M. Tempel et al., INSERTION OF FILAMIN INTO LIPID-MEMBRANES EXAMINED BY CALORIMETRY, THE FILM BALANCE TECHNIQUE, AND LIPID PHOTOLABELING, Biochemistry, 33(42), 1994, pp. 12565-12572
The interaction of the actin-binding protein filamin with mixtures of
zwitterionic and anionic phospholipids (DMPC, DMPG, PC, PS) was studie
d in reconstituted lipid monolayers and bilayers. Protein-lipid intera
ctions were investigated by differential scanning calorimetry, the fil
m balance technique, and hydrophobic photoradiolabeling. For calorimet
ric assays, multilamellar vesicles (MLVs) and large unilamellar vesicl
es produced by the extrusion technique (LUVETs) were used. With MLVs,
filamin induced a pronounced drop in phase transition cooperativity. M
ixed DMPC/DMPG LUVETs showed a linear decrease of the main phase trans
ition enthalpy and a significant shift in temperature for the solidus
and liquidus lines with increasing mole fractions of reconstituted fil
amin. The insertion of native filamin into uncharged and negatively ch
arged lipid monolayers was measured in time/area diagrams with the fil
m balance technique. Finally, we have newly synthesized a highly sensi
tive lipid analogue, [(125)]TID-PC/16, which selectively labels membra
ne-embedded hydrophobic domains of proteins, and which proved to label
filamin, supporting evidence that this protein partially inserts into
the hydrophobic domain of liposomes.