Biophysical insights into a highly selective l‐arginine‐binding lipoprotein of a pathogenic treponeme

• Published in: Protein science Vol. 27; no. 12; pp. 2037 - 2050
• Main Authors: Deka, Ranjit K., Liu, Wei Z., Tso, Shih‐Chia, Norgard, Michael V., Brautigam, Chad A.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.12.2018; Wiley Subscription Services, Inc
• Subjects: ABC transporter; Acids; Amino Acid Sequence; Arginine; Arginine - chemistry; Arginine - metabolism; Binding Sites; Calorimetry; Crystal structure; Crystallization; differential scanning fluorimetry; Fluorimetry; Full‐Length Paper; Full‐Length Papers; Homology; Information systems; isothermal titration calorimetry; Ligands; ligand‐binding protein; Lipoproteins; Lipoproteins - chemistry; Lipoproteins - isolation & purification; Lipoproteins - metabolism; l‐arginine; Metabolism; Models, Molecular; Nutritional requirements; polar amino acids; Protein folding; Protein transport; Proteins; Selectivity; Sequence Alignment; Titration; Titration calorimetry; Treponema; Treponema pallidum - chemistry; X‐ray crystallography; X-ray crystallography; ligand-binding protein; isothermal titration calorimetry; differential scanning fluorimetry; l-arginine; ABC transporter; polar amino acids; Treponema
• ISSN: 0961-8368; 1469-896X
• DOI: 10.1002/pro.3510

Biophysical and biochemical studies on the lipoproteins and other periplasmic proteins from the spirochetal species Treponema pallidum have yielded numerous insights into the functioning of the organism's peculiar membrane organization, its nutritional requirements, and intermediary metabolism. However, not all T. pallidum proteins have proven to be amenable to biophysical studies. One such recalcitrant protein is Tp0309, a putative polar‐amino‐acid‐binding protein of an ABC transporter system. To gain further information on its possible function, a homolog of the protein from the related species T. vincentii was used as a surrogate. This protein, Tv2483, was crystallized, resulting in the determination of its crystal structure at a resolution of 1.75 Å. The protein has a typical fold for a ligand‐binding protein, and a single molecule of l‐arginine was bound between its two lobes. Differential scanning fluorimetry and isothermal titration calorimetry experiments confirmed that l‐arginine bound to the protein with unusually high selectivity. However, further comparison to Tp0309 showed differences in key amino‐acid‐binding residues may impart an alternate specificity for the T. pallidum protein. PDB Code(s): 6DET