Lipid-binding proteins structural motif

In summary, the overall structures of the LBPs have a motif common to a variety of other proteins. Different forms of the /8 barrel have been observed in other lipid-binding proteins as well as in other globular proteins. The unique feature of the LBPs should be visible in Fig. 2. The distinctive feature of the LBPs is their /8-barrel architecture that gives rise to a cavity accommodating a hydrophobic ligand. 

Although the insect lipid-binding protein has the same structural motif as other iLBPs, the side chains used to define the specificity site are somewhat different and appear to include an additional anion (Benning et al., 1992). In addition, the ligand has a different conformation and the overall structure suggests that a different portal might be favored in this protein. 

The amphipathic helix, in which residues are spaced so that the helical periodicity places hydrophobic side chains on one side of the helix and hydrophilic side chains on the other, is a common structural motif used by the peripheral apolipoproteins to bind lipid (Segrest et al., 1992) it is also a structural element present in globular proteins (Perutz et al., 1965). 

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