title: New ouabain-conjugated peptide found from phage displayed peptide library.
abstract: BACKGROUND
  Recently, numerous investigations have shown that endogenous ouabain plays an important role in primary and secondary hypertension. The purpose of this study was to find ouabain-conjugated peptides (OCP) to block or to antagonize actions between endogenous ouabain (EO) and sodium pump, to serve as theoretical and experimental bases of EO in hypertension.
  
  
  METHODS
  The study involved screening the phage displayed 12-peptide library by biopanning for OCP. The DNA sequence of each selected peptide was determined and the amino acid sequences were deduced. The highest consistent of the polypeptide was synthesized by peptide synthesizer. Synthetic OCP was identified, its binding activity determined by radioligand binding assay, and bioactivity of ouabain conjugated peptide was measured by erythrocyte 86Rb uptake.
  
  
  RESULTS
  Three kinds of peptides were identified. Peptide A (12 peptide, Leu-Leu-Ala-Asp-Thr-Thr-His-His-Arg-Pro-Trp-Thr) was the highest consistence of peptide sequences, occupied in 66.7% (8/12). Peptide A was synthesized. The results verified that there was binding activity between synthetically OCP and 3H-ouabain, and that OCP was capable of suppressing the inhibition action between ouabain and sodium pump on the surface of erythrocyte. The results showed that efficacy was in a dose-dependent manner.
  
  
  CONCLUSIONS
  It is important that the results not only obtain distinctive OCP, but also supply valuable experimental data in detection of ouabain and therapy in hypertension.
authors.affiliation: Department of Cardiology, the Second Hospital and School of Medicine, Xi'an Jiao Tong University, Xi'an, People's Republic of China. zhangmingjuanyj@yahoo.com
authors.forename: Ming-juan
authors.initials: MJ
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: Zhuo-ren
authors.initials: ZR
authors.lastname: Lu
mesh_terms: D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000008:administration & dosage* / Q000378:metabolism; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D010042:Ouabain / Q000008:administration & dosage* / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010047:Ovalbumin / Q000008:administration & dosage; D010446:Peptide Fragments / Q000187:drug effects / Q000378:metabolism; D019151:Peptide Library; D010455:Peptides / Q000187:drug effects* / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D019151:Peptide Library; D010455:Peptides; D010042:Ouabain; D010047:Ovalbumin