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Free keywords:
Amino Acid Sequence
Binding Sites
Biological Transport
Carrier Proteins/*chemistry/genetics/metabolism
Cloning, Molecular
Crystallography, X-Ray
Escherichia coli/genetics/metabolism
Gene Expression
Genetic Vectors/chemistry/metabolism
Humans
Intracellular Signaling Peptides and Proteins/*chemistry/genetics/metabolism
Mitochondrial Proteins/*chemistry/genetics/metabolism
Models, Molecular
Phosphatidic Acids/*chemistry/metabolism
Phosphatidylserines/*chemistry/metabolism
Protein Binding
Protein Conformation, alpha-Helical
Protein Conformation, beta-Strand
Protein Interaction Domains and Motifs
Protein Isoforms/chemistry/genetics/metabolism
Recombinant Proteins/chemistry/genetics/metabolism
Saccharomyces cerevisiae/genetics/metabolism
Saccharomyces cerevisiae Proteins/*chemistry/genetics/metabolism
Sequence Alignment
Sequence Homology, Amino Acid
Substrate Specificity
Abstract:
Conserved lipid transfer proteins of the Ups/PRELI family regulate lipid accumulation in mitochondria by shuttling phospholipids in a lipid-specific manner across the intermembrane space. Here, we combine structural analysis, unbiased genetic approaches in yeast and molecular dynamics simulations to unravel determinants of lipid specificity within the conserved Ups/PRELI family. We present structures of human PRELID1-TRIAP1 and PRELID3b-TRIAP1 complexes, which exert lipid transfer activity for phosphatidic acid and phosphatidylserine, respectively. Reverse yeast genetic screens identify critical amino acid exchanges that broaden and swap their lipid specificities. We find that amino acids involved in head group recognition and the hydrophobicity of flexible loops regulate lipid entry into the binding cavity. Molecular dynamics simulations reveal different membrane orientations of PRELID1 and PRELID3b during the stepwise release of lipids. Our experiments thus define the structural determinants of lipid specificity and the dynamics of lipid interactions by Ups/PRELI proteins.
