title: Identification of hydrophobic residues critical for DPP-IV dimerization.
abstract: The prolyl dipeptidase DPP-IV plays diverse and important roles in cellular functions. It is a membrane-bound exoprotease involved in the proteolytic cleavage of several insulin-sensing hormones. The inhibition of its enzymatic activity has been proven effective in the treatment of type II diabetes. Homodimeric DPP-IV interacts extracellularly with adenosine deaminase, and this interaction is critical for adenosine signaling and T-cell proliferation. In this study, we investigated the contribution of hydrophobic interactions to the dimerization of DPP-IV. Hydrophobic residues F713, W734, and Y735 were found to be essential for DPP-IV dimerization. Moreover, the enzymatic activity of DPP-IV was correlated with its quaternary structure. Monomeric DPP-IV had only residual activity left, ranging from 1/30 to 1/1600 of the dimeric forms. Using a surface plasmon resonance technique, we demonstrated that the affinity of these DPP-IV monomers for adenosine deaminase was not significantly altered, compared to that of dimeric DPP-IV. The study not only identifies the hydrophobic interactions critical for DPP-IV dimer formation, but also reveals no global conformational change upon the formation of monomers as determined by the protein-protein interaction (Kd) of DPP-IV with adenosine deaminase.
authors.affiliation: Division of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Miaoli 350, Taiwan, ROC.
authors.forename: Chia-Hui
authors.initials: CH
authors.lastname: Chien
authors.forename: Chia-Hua
authors.initials: CH
authors.lastname: Tsai
authors.forename: Chun-Hung
authors.initials: CH
authors.lastname: Lin
authors.forename: Chi-Yuan
authors.initials: CY
authors.lastname: Chou
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D019281:Dimerization; D018819:Dipeptidyl Peptidase 4 / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids; D020836:Protein Structure, Quaternary; D017386:Sequence Homology, Amino Acid; D020349:Surface Plasmon Resonance; D014461:Ultracentrifugation
chemical_list: D018819:Dipeptidyl Peptidase 4