title: Packing contacts can mediate highly specific interactions between artificial transmembrane proteins and the PDGFbeta receptor.
abstract: We used proteins with randomized transmembrane (TM) domains to explore the role of hydrophobic amino acids in mediating specific interactions between transmembrane helices. The 44-aa bovine papillomavirus E5 protein, which binds to the TM domain of the PDGFbeta receptor (PDGFbetaR) was used as a scaffold to construct a library encoding small dimeric proteins with randomized, strictly hydrophobic TM domains, and proteins were selected that induced focus formation in mouse C127 cells by activating the PDGFbetaR. Analysis of these proteins identified a motif of two hydrophobic residues that, when inserted into a 17-residue polyleucine TM domain, generated a protein that activated the PDGFbetaR and transformed cells. In addition, we identified transforming proteins that activated the wild-type PDGFbetaR but did not activate a series of PDGFbetaR TM point mutants that were efficiently activated by the E5 protein, indicating that these proteins were more specific than the E5 protein. Our results implied that multiple van der Waals interactions distributed along the entire length of the TM domains were required for productive interaction between the PDGFbetaR and some small proteins lacking hydrophilic TM residues. Our results also suggested that excluding hydrophilic residues from small TM proteins and peptides is a strategy to increase the specificity of heteromeric TM helix-helix interactions.
authors.affiliation: Department of Genetics and Therapeutic Radiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA.
authors.forename: Jennifer B
authors.initials: JB
authors.lastname: Ptacek
authors.forename: Anne P B
authors.initials: AP
authors.lastname: Edwards
authors.forename: Lisa L
authors.initials: LL
authors.lastname: Freeman-Cook
authors.forename: Daniel
authors.initials: D
authors.lastname: DiMaio
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000596:Amino Acids; D000818:Animals; D002472:Cell Transformation, Viral; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009856:Oncogene Proteins, Viral / Q000737:chemistry; D011485:Protein Binding; D025941:Protein Interaction Mapping; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D000596:Amino Acids; D008565:Membrane Proteins; D009856:Oncogene Proteins, Viral; C054304:oncogene protein E5, Bovine papillomavirus type 1; D020797:Receptor, Platelet-Derived Growth Factor beta