title: A structural biology approach to understand human lymphatic filarial infection.
abstract: The presence of aspartic protease inhibitor in filarial parasite Brugia malayi (Bm-Aspin) makes it interesting to study because of the fact that the filarial parasite never encounters the host digestive system. Here, the aspartic protease inhibition kinetics of Bm-Aspin and its NMR structural characteristics have been investigated. The overall aim of this study is to explain the inhibition and binding properties of Bm-Aspin from its structural point of view. UV-spectroscopy and multi-dimensional NMR are the experiments that have been performed to understand the kinetic and structural properties of Bm-Aspin respectively. The human aspartic proteases that are considered for this study are pepsin, renin, cathepsin-E and cathepsin-D. The results of this analysis performed with the specific substrate [Phe-Ala-Ala-Phe (4-NO2)-Phe-Val-Leu (4-pyridylmethyl) ester] against aspartic proteases suggest that Bm-Aspin inhibits the activities of all four human aspartic proteases. The kinetics studies indicate that Bm-Aspin follows a competitive mode of inhibition for pepsin and cathepsin-E, non-competitive for renin and mixed mode for cathepsin-D. The triple resonance NMR experiments on Bm-Aspin suggested the feasibility of carrying out NMR studies to obtain its solution structure. The NMR titration studies on the interactions of Bm-Aspin with the proteases indicate that it undergoes fast-exchange phenomena among themselves. In addition to this, the chemical shift perturbations for some of the residues of Bm-Aspin observed from (15)N-HSQC spectra upon the addition of saturated amounts of aspartic proteases suggest the binding between Bm-Aspin and human aspartic proteases. They also provide information on the variations in the intensities and mode of binding between the proteases duly corroborating with the results from the protease inhibition assay method.
authors: Claflin University, Department of Chemistry, Orangeburg, South Carolina, United States of America ; University of Madras, CAS in Crystallography and Biophysics, Chennai, Tamil Nadu, India.
authors: Raghavendra Sashi Krishna
authors: RS
authors: Nagampalli
authors: University of Madras, CAS in Crystallography and Biophysics, Chennai, Tamil Nadu, India.
authors: Krishnasamy
authors: K
authors: Gunasekaran
authors: Anna University, Centre for Biotechnology, Chennai, Tamil Nadu, India.
authors: Rangarajan Badri
authors: RB
authors: Narayanan
authors: Claflin University, Department of Chemistry, Orangeburg, South Carolina, United States of America.
authors: Angela
authors: A
authors: Peters
authors: Claflin University, Department of Chemistry, Orangeburg, South Carolina, United States of America.
authors: Rajagopalan
authors: R
authors: Bhaskaran
mesh_terms: D000818:Animals; D057055:Aspartic Acid Proteases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D017178:Brugia malayi / Q000737:chemistry* / Q000502:physiology*; D015801:Helminth Proteins / Q000737:chemistry* / Q000378:metabolism; D006790:Host-Parasite Interactions / Q000502:physiology*; D006801:Humans; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding
chemical_list: D015801:Helminth Proteins; D057055:Aspartic Acid Proteases