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Site-Directed Mutagenesis to Identify Key Residues in Structure-Function Relationship of Winged Bean Chymotrypsin-Trypsin Inhibitor and 3-D Structure Prediction

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Abstract:

Winged bean chymotrypsin trypsin inhibitor (WbCTI) is a Kunitz type serine protease inhibitor that inhibits both trypsin and chymotrypsin at 1:1 molar ratio. Site-directed mutagenesis study was employed to generate two mutants of WbCTI, with an aim to explore its dual inhibitory properties against the proteases. The mutants were expressed in Escherichia coli and, were purified to homogeneity using a single step immunoaffinity column. The two mutants, each containing a single mutation at the amino acid sequence positions of 63 and 64, were named as L63A and R64A, respectively. Purified L63A-WbCTI exhibited anti-trypsin activity with no anti-chymotrypsin activity whereas R64A-WbCTI could inhibit chymotrypsin but not trypsin. To investigate the binding interactions between the mutated forms of WbCTI with the putative proteases, binding studies were carried out using gel filtration chromatography which further confirmed the formation of enzyme-inhibitor complexes. Finally, 3D model structure of WbCTI was designed using computer simulations which further emphasize the roles of L63 and R64 residues for dual inhibitory characteristics of WbCTI.





Keywords: 3-D Structure Prediction; Biosym Technologies; ETI; IPTG; LB-ampicillin agar; Molecular modeling; PCR; Plant proteinase inhibitors (PI); Site Directed Mutagenesis; WbCTI mutants; bacterial lysate; chromatography; reactive site loop; serine protease inhibitor; trypsin and chymotrypsin

Document Type: Research Article

DOI: https://doi.org/10.2174/092986611794927901

Publication date: 2011-05-01

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  • Protein & Peptide Letters publishes short papers in all important aspects of protein and peptide research, including structural studies, recombinant expression, function, synthesis, enzymology, immunology, molecular modeling, drug design etc. Manuscripts must have a significant element of novelty, timeliness and urgency that merit rapid publication. Reports of crystallisation, and preliminary structure determinations of biologically important proteins are acceptable. Purely theoretical papers are also acceptable provided they provide new insight into the principles of protein/peptide structure and function.
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