Fourier-transform infrared studies of calcium-ATPase partitioning in phospholipid mixtures of 1,2-dipalmitoylphosphatidylcholine-d62 with 1-palmitoyl-2-oleoylphosphatidylethanolamine and 1-stearoyl-2-oleoylphosphatidylcholine

Abstract

CaATPase from rabbit sarcoplasmic reticulum has been reconstituted into binary lipid mixtures of 1-palmitoyl-2-oleoylphosphatidylethanolamine (POPE)/1,2-dipalmitoylphosphatidylcholine-d62 (DPPC-d62) and 1-stearoyl-2-oleoylphosphatidylcholine (SOPC)/DPPC-d62. Fourier-transform infrared (FT-IR) spectroscopy has been used to monitor temperature-induced structural alterations in the individual lipid components in the presence and absence of protein. A simple two-state model is used to construct a phase diagram that is in good agreement with one constructed from differential scanning calorimetry data, for the POPE/DPPC-d62 (protein-free) system. Although these two lipids are miscible over at least most of the composition range, substantial deviations from ideal behavior are observed. An estimate of the nonideality of mixing in both the gel and liquid-crystalline phases is obtained from regular solution theory. The phase diagram for SOPC/DPPC-d62 shows gel-phase immiscibility. FT-IR studies of ternary (POPE/DPPC-d62/CaATPase) complexes indicate that both lipid components are disordered by protein at all temperatures studied. In addition, their melting events are broadened and shifted to lower temperatures compared with the appropriate binary lipid mixture. Semiquantitative estimates for the fraction of each lipid melted are obtained from the model. The effect of protein on SOPC/DPPC-d62 mixtures depends on that total lipid to protein ratio. At low protein levels, SOPC is preferentially selected by CaATPase, so that bulk lipid is enriched in DPPC-d62. At high levels of protein, both lipid components are selected. The applicability of vibrational spectroscopy for determination of the partitioning preferences of membrane proteins into regions of particular chemical structure or physical order in a complex lipid environment is demonstrated.

Lipid composition, membrane structure relationships in lens and muscle sarcoplasmic reticulum membranes

“…The same result was found for the hydrocarbon chain order of a delipidated sample containing mostly lipids in contact with the pump (Table II). These results are similar to the results of Jaworsky and Mendelsohn 75 who showed that in ternary synthetic lipid complexes the Ca 2ϩ -ATPase pump disorders the lipid hydrocarbon chains broadening the phase transition and shifting it to lower temperatures. Soleus lipid hydrocarbon chain order was not changed significantly by the Ca 2ϩ -ATPase [ Fig.…”

Infrared studies of protein-induced perturbation of lipids in lipoproteins and membranes

“…However, in lipid mixtures that mix well such as POPE/DPPC-d 62 no preferential selection of the lipids towards the protein is seen (Mendelsohn et al, 1984b). The relationship between lipid miscibility and preferential effect of protein in a lipid mixture was later confirmed in a study of the effect of Ca 2 + -ATPase on SOPC/ DPPC-d 62 (Jaworsky and Mendelsohn, 1985). The intrinsic protein apocytochrome c affects a mixture of DMPC-d 54 /DMPG in a similar fashion for both lipids (Muga et al, 1991), but the effect upon DMPG is greatly attenuated when compared to the effect of apocythchrome on DMPG alone.…”

Protective effects of sorbitol during the vacuum drying of Lactobacillus helveticus: an FT-IR study

“…The smaller wavenumber increase and higher onset frequency of the band 2850 can be due to the presence of the membrane proteins and glycolipids, which are still the integral components in whole cells of L. helveticus. The membrane proteins and glycolipids were shown to disorder the organization of synthetic membrane vesicles and cause a smaller wavenumber increase Hincha 2003, 2005) and higher onset frequency of the band 2850 (Jaworsky and Mendelsohn 1985).…”