Site-specific protein backbone and side-chain NMR chemical shift and relaxation analysis of human vinexin SH3 domain using a genetically encoded 15N/19F-labeled unnatural amino acid

SH3 is a ubiquitous domain mediating protein–protein interactions. Recent solution NMR structural studies have shown that a proline-rich peptide is capable of binding to the human vinexin SH3 domain. Here, an orthogonal amber tRNA/tRNA synthetase pair for 15N/19F-trifluoromethyl-phenylalanine (15N/19F-tfmF) has been applied to achieve site-specific labeling of SH3 at three different sites. One-dimensional solution NMR spectra of backbone amide (15N)1H and side-chain 19F were obtained for SH3 with three different site-specific labels. Site-specific backbone amide (15N)1H and side-chain 19F chemical shift and relaxation analysis of SH3 in the absence or presence of a peptide ligand demonstrated different internal motions upon ligand binding at the three different sites. This site-specific NMR analysis might be very useful for studying large-sized proteins or protein complexes.

Research highlights
► Chemical synthesis of 15N/19F-trifluomethyl phenylalanine.
► Site-specific incorporation of 15N/19F-trifluomethyl phenylalanine to SH3.
► Site-specific backbone and side chain chemical shift and relaxation analysis.
► Different internal motions at different sites of SH3 domain upon ligand binding.