Molecular Biophysics Unit, IISc., Bangalore

Dept. of Biological Chemistry, Weizmann Institute of Science, Israel

Biology Division, University of California at San Diego, USA

CDRI incentive awards on its Annual Day (each year on 17th Feb) in the year 2004, 2005, 2007 and 2012 (two) for publishing in high impact factor journal.

Sir Charles Clore postdoctoral fellowship for two years in Weizmann Institute of Science, Israel.

Our broad area of research is “Structure-function studies of membrane-associated proteins and peptides and design of bioactive peptides”.  So far we have worked on understanding the structure-function relationships in pore-forming toxin, naturally occurring antimicrobial peptides and KvAP, K+ channel and on the design of novel cell-selective antimicrobial peptides and characterization of anti-endotoxin properties of antimicrobial peptides.  By synthesizing the conserved segments from these proteins and peptides, we are trying to identify and characterize their important structural and functional elements.  Our work has contributed in understanding the basis of cytotoxicity in a pore-forming toxin, hemolysin E and naturally-occurring antimicrobial peptides and we have designed novel cell-selective peptides which could be potential lead molecules for the development of novel antimicrobial drugs.  We have shown novel peptide engineering by utilizing leucine zipper sequences for design of antimicrobial peptides with reduced toxicity. Very recently we have demonstrated the crucial role of this structural element in neutralization of lipopolysaccharide–induced pro-inflammatory response in macrophage cells by the bee venom antimicrobial peptide, melittin.  Our recent results showed a weakly voltage-sensitive ion channel property of a 22-residue S6 segment derived peptide which comprises the inner lining of the pore region of voltage-gated, KvAP channel.  Recently, we have identified a single amino acid substitution in 13-residue scorpion antimicrobial peptide, IsCT that transformed it into a cell-penetrating peptide with intracellular target in bacteria. We have designed new variants of self-assembling peptide, KLD-12 in order to introduce antimicrobial attribute in it so that it can fight against secondary infection which is a common occurrence during the external application of such tissue-engineering biomaterial. At least one of the new designed variants showed better fracture healing in vivo animal model. At present we are also trying to design novel osteogenic and anti-diabetic peptides. The methodology of our work includes various chemical, biophysical and cell biological approaches; for example: solid phase peptide synthesis, fluorescent labeling of these peptides; purification of labeled and unlabeled peptides by HPLC, variety of fluorescence, circular dichroism, FACS and confocal microscopic studies; assay of bactericidal and cytotoxic activity of the peptides, cell culture, cytokine assays, detection of different proteins of interests in the cells etc.  Our long-term goal is to design peptides/peptidomimetics of pharmacological importance.

Specific Interests:

• Structure-Function Studies on naturally occurring antimicrobial peptides and design of their novel analogs with higher therapeutic potential.

• Design of totally novel peptides with cell-selective activity and investigation on their biological activity against different microorganisms.

• Understanding the amino acid sequence requirement for the anti-endotoxin properties of peptides and design of novel peptides with anti-endotoxin properties.

• Synthetic peptide model to understand the structure-function relationships of membrane-associated proteins.

• Identification and characterization of important segments from proteins, involved with pathogenesis of diseases.

1. Identification of a leucine zipper like sequence in bee venom antimicrobial peptide, melittin   and design of its analogs to characterize its role. Heptadic amino acids are marked in bold, whereas mutated amino acids are marked as bold and underlined.
   

1. Helical wheel projections of the first 21 amino acids of melittin and its analog,  MM-2

              Effect of mutation in the leucine zipper motif of melittin on its hemolytic activity 
               (a), MM-1 (b), and MM-2 (c) against human red blood cells.
                (JBC.2004. Vol. 279, No. 53. pp.  55042)

Detection of localization of the Rho-labeled melittin, (L9A) melittin, (L9,16A) melittin, and melittin scrambled onto hRBCs and E. coli 10536 cells by confocal microscopy (Biochemistry 2010, 49, 7920)

Determination of the affinity of the NBD-labelled magainin 2 and Mag-mut (0.2 μM) to zwitterionic lipid vesicles, as detected by titration with PC/Chol lipid vesicles.
(Biochem. J. (2011) 436, 609)

(A) Binding curve of magainin 2. (B) Binding isotherm of magainin 2.
         (C) Binding curve of Mag-mut. (D) Binding isotherm of Mag-mut.

Continuous current traces of ion channel formed by S6 peptide on BLM at voltages +100 (A) and -100 mV (C) and corresponding histograms, B and D, respectively (carried out in collaboration with Prof. Subhendu Ghosh’s Lab at Biophysics Div. Delhi University South Campus)... (JBC.2011.VOL. 286, NO. 28, pp. 24828)

Expression level of iNOS and TNF-α in LPS-stimulated cells in the presence of melittin and its analogues.(JBC.2012. VOL. 287, NO. 3, pp. 1980)

Determination of environment of the tryptophan residues of peptides (LRP, VRP, FRP, ARP) in their membrane-bound states by recording their emission maxima and by Stern−Volmer plots for acrylamide quenching of tryptophan fluorescence in the presence of different lipid vesicle. (J Med Chem. 2013;56(3):924-39)