title: Structural adaptation of the glycophorin A transmembrane homodimer to D-amino acid modifications.
abstract: Protein-protein recognition is an essential process in life. The chemistry of these kind of interactions is predominantly stereospecific (i.e. receptor-ligand, antibody-hapten binding). Here, we investigated whether the hydrophobic nature of the membrane affects this stereospecificity. To this end, we synthesized a diastereomer analogue (2D-GPA) of the glycophorin A transmembrane helix, with two l-valine residues replaced by their d-enantiomer. This ensures a disruption of the secondary structure. We investigated the ability of the diastereomer peptide to recognize the GPA chimera in the ToxR homodimer reporting system, in vivo. The peptide demonstrated a dose-dependent dominant negative effect on the GPA transmembrane in the bacterial ToxR system, suggesting a wild-type like interaction. This result was corroborated in vitro by fluorescence energy transfer between 2D-GPA and all-l GPA. Peptide binding to the bacteria was confirmed through confocal imaging, and Western blot confirmed that ToxR GPA receptor levels are not affected by the presence of the exogenous peptide. In order to understand the structural basis for heterodimer formation, homodimer and heterodimer structures, based on the NMR 3D structure of GPA, were subjected to a molecular dynamics simulation. The resulting heterodimer structure maintained most of the original inter-helical interactions, and its structure is similar to that of the homodimer. We postulate that the need to satisfy all H-bonds can compensate for the structural strain induced by the presence of the d-amino acid residues.
authors.affiliation: Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Doron
authors.initials: D
authors.lastname: Gerber
authors.forename: Neta
authors.initials: N
authors.lastname: Sal-Man
authors.forename: Yechiel
authors.initials: Y
authors.lastname: Shai
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism; D006021:Glycophorins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D010446:Peptide Fragments / Q000737:chemistry*; D011485:Protein Binding / Q000502:physiology*; D011487:Protein Conformation; D017510:Protein Folding; D013237:Stereoisomerism; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D006021:Glycophorins; D010446:Peptide Fragments; D014157:Transcription Factors; C066719:toxR protein, bacteria