Molecular examination of the transmembrane requirements of the platelet-derived growth factor β receptor for a productive interaction with the bovine papillomavirus E5 oncoprotein

Abstract

The small transmembrane E5 protein of bovine papillomavirus (BPV) transforms cells by forming a stable complex with and activating the platelet-derived growth factor β receptor (PDGFβR). The E5/PDGFβR interaction is thought to involve specific physical contacts between the transmembrane domains of the two proteins. Lys499 at the extracellular juxtamembrane position and Thr513 within the transmembrane domain of the PDGFβR are required for the interaction and are predicted to contact analogously positioned residues in the E5 protein. Here, mutagenic analysis of the transmembrane region of the PDGFβR was performed to further characterize the nature of the E5/PDGFβR interaction. We show that the receptor transmembrane domain, with minimal extracellular and intracellular sequence, is sufficient for the interaction. In addition, we provide evidence that the polar nature of Thr513 as well as its positioning along the transmembrane α-helix is important for the interaction. We also identify the receptor transmembrane amino acids Ile506 and Leu520 as additional requirements for the interaction. Because Lys499, Thr513, Ile506, and Leu520 all align along the same face of the predicted PDGFβR transmembrane α-helix, our data support the model that the PDGFβR contacts the E5 protein via multiple amino acids along a single α-helical interface.