The Use of Liprotides To Stabilize and Transport Hydrophobic Molecules

Abstract

Recently, it has been shown that different complexes consisting of protein and fatty acids, which we call liprotides, have common functional and structural features. Liprotides can transfer their fatty acid content to membranes, highlighting the potential to incorporate other small molecules and help transfer them to membranes. In this study, this potential was explored with regard to the poorly water-soluble vitamin E compound α-tocopherol (Toc). Uptake into liprotides increased Toc solubility and chemical stability. The liprotide-Toc complexes retained the characteristic liprotide structure with a core of fatty acid surrounded by protein. Toc and fatty acid could be transferred to artificial vesicles upon being incorporated into the liprotide complex. Extending this work, we found that free tryptophan and the vitamin A precursor retinaldehyde could also be incorporated in the liprotides; however, other small molecules failed to be taken up, and we conclude that successful incorporation requires a hydrophobic terminal moiety that can be accommodated within the micelle interior of the liprotides. Nevertheless, our work suggests that liprotides are able to stabilize and transport a number of otherwise insoluble small molecules with significant potential health benefits.

Liprotides assist in folding of outer membrane proteins

“…Since much of the OA in solution should be bound in the complex at these concentrations, folding is most likely limited by having a too small tOmpA:OA ratio rather than by having too much free OA in solution. Data from SAXS suggest that each liprotide contains around 30 OA molecules, in good agreement with earlier findings . Since around 40 OA molecules per tOmpA is needed to achieve a 50% folding it is likely that folding of tOmpA required more than one liprotide or that one liprotide can provide extra OA to another liprotide to assist in OmpA folding.…”

“…In the liprotides, OA is covered by a protein shell which mediates OA's contact with its surroundings. Earlier studies have shown that the liprotides can easily interact with membranes and transfer its OA content . To test the effect of the liprotide protein shell on tOmpA folding kinetics, we compared folding rates of tOmpA in liprotide, DDM and small unilamellar vesicles (SUV) of DLPC (Fig.…”

“…Circular dichroism (CD) and Trp fluorescence have shown that aLA upon liprotide formation undergoes large tertiary structural changes in conjunction with smaller changes in secondary structure . Liprotides kill cancer cells but not healthy differentiated cells, have antibacterial properties and can stabilize and solubilize small hydrophobic compounds . OA is generally not soluble at neutral pH but the protein shell helps to solubilize the lipid component .…”

Role of Charge and Hydrophobicity in Liprotide Formation: A Molecular Dynamics Study with Experimental Constraints

“…Additional binding occurs at higher [OA], however, and at the third point (halfway between point 2 and the baseline, set to 0 kcal mol −1 ) we see binding of 21.6±1.8 OA/aLA. Remarkably, this ratio corresponds to that seen with liprotides when large amounts of OA are mixed with aLA and separated by gel filtration (21±5 OA/aLA) . At all three transitions, the amount of unbound OA was essentially zero within error ( y ‐axis intercept in Figure B and Table S2), thus confirming that all of the OA complexes with aLA.…”

Proteins in a brave new surfactant world

“…In a complementary version of the protein:fluorinated surfactant complexes, liprotides transfer fatty acids to membranes while proteins are released 49 , which is probably the basis for their biological activity. This transfer ability highlights their possible use as host-guest systems for the transport of hydrophobic and sensitive molecules such as vitamins 50 which can be solubilized in the micellar interior. The elucidation of liprotide structures provides a remarkable link between the physical-chemical world of protein-surfactant complexes and biologically potent agents.…”