alpha-Actinin interacts specifically with model membranes containing glycerides and fatty acids

A method was developed to identify specific protein-lipid interactions of complex lipid mixtures and to assess their effect upon the arrangement of such complexes in monolayers at an air-water interface. Its application to striated muscle alpha-actinin revealed that just two lipids selectively interact with alpha-actinin. One molecule of glyceride and one molecule of fatty acid were found to be associated in a constant stoichiometry with one molecule of the alpha-actinin dimer. In the presence of both glycerides and fatty acids unexpectedly rigid monolayer areas formed. This lipid specificity could be confirmed by brief protease digestion of alpha-actinin liposome mixtures followed by peptide analysis; the peptide patterns of alpha-actinin depended on the presence or absence of only these two lipids. Possible implications of these findings are discussed in the context of Z-line formation.