NMR structural studies of membrane active peptides and proteins
Date of Issue2014
School of Biological Sciences
Large number of biological activities across cell membrane occurs through special proteins present in membrane milieu. These can be cell-cell interactions, transportation of electrons, chemicals and signal transduction. Immense development in structural biology and biochemistry has contributed to our understanding of structure, folding, stability and function of water soluble proteins, while similar knowledge of membrane counter parts is greatly lacking. This limited success owes to certain characteristics like insolubility and aggregation in the absence of membrane mimetic environment like detergents. Designing the proteins that would fold correctly with specifically defined interactions in the membrane environment is principal test of our learning related to protein engineering. This is arguably the most challenging task in protein science. Towards this, we have succcessfully constructed two different set of peptides i.e. α-helix and β-hairpin (a monomeric unit of β-sheet). VK22 is a helical peptide is used as a template for directed evolution by Ala scanning mutagenesis. Several polar and positively charged residues from the peptide were systematically replaced by Alanine to increase the hydrophobicity of the peptides and to reduce the complexity of system. Later on, substitution of Tyr-16 with His (TM-His) made the peptide specific for heme binding and catalytic activity in DPC micelles. IV-8 is a model peptide composed of 8 amino acid residues with two residue turn. The turn (type-II’) is introduced with DPro-Gly at position 4 and 5, respectively. This peptide forms β- hairpin in DPC micelles and catalyzes hydrogen peroxide with specific velocity of 1620 Abs450 S-1M-1. SARS-CoV infection is mediated by fusion of Spike (S2) glycoprotein with target cell receptor eventually leads to its internalization. Different regions in glycoprotein have the ability to destabilize and interact with cell membrane. However, much progress has been achieved in understanding the mechanisms of membrane fusion, still structure of fusion proteins need to be elucidated to decipher the basis of virus-host fusion process. In view of this, we have determined the structure of these membrane active peptides in membrane environment (DPC micelles).