![Figure 2. GMAPN, but not α-synuclein, is a sensor of the curvature of neutral lipid membranes. (A and B) Structural features of the ALPS motif of GMAP-210 (aa 1–38) and of the α-synuclein AH and principles of the liposome-binding experiments. (A) The ALPS motif of GMAP-210 is assumed to form a perfect α helix. The structure of α-synuclein is from recent electron paramagnetic resonance experiments (Jao et al., 2008). (B) For clarity, only two 11-mer repeats (aa 9–30) are shown, but the remainder of the AH displays the same features. Yellow: Ala, Val, Leu, Ile, Met, Phe, and Trp. Pink: Ser, Thr, and Gly. Red: Asp and Glu. Blue: Lys and Arg. Green: other residues. To monitor lipid binding, the constructs were labeled with NBD on a cysteine at the beginning of the AH (mutations M1C in GMAPN and V3C in α-synuclein). The drawing is approximately to scale for a liposome of radius (R) = 30 nm. (C and D) Emission fluorescence spectra of [NBD]GMAPN (C) or [NBD]α-synuclein (D; 125 nM each) with or without calibrated neutral liposomes obtained by extrusion through polycarbonate filters of defined pore size or sonication (150 µM phospholipids; egg PC/POPE = 7:3; cholesterol/phospholipids = 1:5). (top insets) Fluorescence level at 530 nm as a function of liposome radius (as determined by dynamic light scattering). The horizontal lines indicate the fluorescence level in the absence of liposomes. (C, bottom inset) Fluorescence at 530 nm of 125 nM [NBD]GMAPN as a function of phospholipid concentration. Color coding for sonicated and extruded liposomes is indicated on the left. Calculation of partition coefficients is as previously described (see Materials and methods; Mesmin et al., 2007). N, N terminus; C, C terminus.](https://cdn.rupress.org/rup/content_public/journal/jcb/194/1/10.1083_jcb.201011118/5/jcb_201011118r_rgb_fig2.jpeg?Expires=1773573873&Signature=V33pyEbEj7FFL1LvZYT~nUgFrjbZnnshb0l4NDMuA8DsGFHmP2cCsgE-pA7O1Mv1DbNZNMZi284Y5owv03icPfKdl~rPDCiLu5ifTaKqEBjSpuVaB~yFHcbqKQ8-x532rSUoAW3EuCBzod1GMXo7aDg8Kf1l-oofidVmPMrNPtgZs4yL1h~h2qh6QH4n0bGepROPd9aCc3-nJLUum~ltJPTlLdDAfY64qn3F7w6-~uq3txxZBMbrWWpcdxWNB~Nr0nAuYc7zcU9B5B~rE6SH58e8DibzvmwSMHiN9QmRAOGZcadyln9~LJeioZ0vMmlrtKHshTZYaWY-5VJXyEIFBA__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
GMAPN, but not α-synuclein, is a sensor of the curvature of neutral lipid membranes. (A and B) Structural features of the ALPS motif of GMAP-210 (aa 1–38) and of the α-synuclein AH and principles of the liposome-binding experiments. (A) The ALPS motif of GMAP-210 is assumed to form a perfect α helix. The structure of α-synuclein is from recent electron paramagnetic resonance experiments (Jao et al., 2008). (B) For clarity, only two 11-mer repeats (aa 9–30) are shown, but the remainder of the AH displays the same features. Yellow: Ala, Val, Leu, Ile, Met, Phe, and Trp. Pink: Ser, Thr, and Gly. Red: Asp and Glu. Blue: Lys and Arg. Green: other residues. To monitor lipid binding, the constructs were labeled with NBD on a cysteine at the beginning of the AH (mutations M1C in GMAPN and V3C in α-synuclein). The drawing is approximately to scale for a liposome of radius (R) = 30 nm. (C and D) Emission fluorescence spectra of [NBD]GMAPN (C) or [NBD]α-synuclein (D; 125 nM each) with or without calibrated neutral liposomes obtained by extrusion through polycarbonate filters of defined pore size or sonication (150 µM phospholipids; egg PC/POPE = 7:3; cholesterol/phospholipids = 1:5). (top insets) Fluorescence level at 530 nm as a function of liposome radius (as determined by dynamic light scattering). The horizontal lines indicate the fluorescence level in the absence of liposomes. (C, bottom inset) Fluorescence at 530 nm of 125 nM [NBD]GMAPN as a function of phospholipid concentration. Color coding for sonicated and extruded liposomes is indicated on the left. Calculation of partition coefficients is as previously described (see Materials and methods; Mesmin et al., 2007). N, N terminus; C, C terminus.
