SINP Triennial Report - Saha Institute of Nuclear Physics

Biophysical Sciences Including Chemistry 3
properties take place in a bacterial system subsequent to a radiation exposure. It was found
that these two properties were selectively expressed into the bacterial system depending
on the nature and extent of DNA damage inflicted in the system. Studies on the effect of
four other spices in a bacterial system are also being undertaken.
The studies on the environmental impact on Rhizobium sp. cells revealed that different
fertilisers and pesticides have detrimental effect on growth and ultra structure of Rhizobium
sp. cells in liquid culture medium.
Crystallography & Molecular Biology
Members of the Crystallography & Molecular Biology (C&MB) Division are engaged in
broader research areas of (a) macromolecular crystallography and (b) cellular and molecular
biology for understanding biological processes in cancer, infectious diseases and
Huntington's disease (HD). In macromolecular crystallography, the major activities center
on cloning, expression, purification, crystallization and determination of protein structures
using X-ray diffraction and other spectroscopic techniques. Structure based protein
engineering approaches have been used to enhance the stability and to impart collagenolytic
activity in papain, and enhance catalytic efficiency of ervatamin-C, a thermostable protease
belonging to the papain family. Protein structures complexed with the substrates/inhibitors/
drug have also been solved. Various cell and molecular biology techniques are used to
decipher the signaling pathways in Entamoeba histolytica, mRNA turn over in Leishmania
donovani and telomerase regulation in mammalian cells in culture. Similar techniques are
used to determine mechanism(s) of transcriptional deregulation either by HIPPI or by
deregulation micro RNA in HD model.
Macromolecular crystallography
Cloning, expression, purification and preliminary X-ray diffraction analysis of Psu, an
inhibitor of the bacterial transcription terminator Rho and CheY3, a response regulator
that directly interacts with the flagellar 'switch complex' in Vibrio cholerae have been
reported. Through crystal structure and biochemical studies on three chimeric proteins
ECI (L)-WCI(S), ETI(L)-WCI(S), and STI(L)-WCI(S), where the inhibitory loop of ECI,
ETI, and STI is placed on the scaffold of their homolog WCI, a set of novel scaffolding
residues have been identified that remotely controls the inhibitory property so much so
that a set of loop residues (SRLRSAFI) offering strong trypsin inhibition in ETI, act as a
substrate when they seat on the scaffold of WCI i. e. in ETI(L)-WCI(S). Absence of these
three novel scaffolding residues Trp88, Arg74, and Tyr113 makes the inhibitory loop flexible
in ETI(L)-WCI(S) leading to a loss of canonical conformation, explaining its substratelike
behavior. Incorporation of this barrier back in ETI(L)-WCI(S) through mutations
increases its inhibitory power, supporting our proposition. Analysis of the structure of
NP24-I, a thaumatin-like protein, explains its glucanase and allergenic properties. Structures
of cyclophilin from Leishmania donovani at 1.97 Å resolution and the complex of
cyclophilin with cyclosporin at 2.6 Å resolutions have been solved.
Crystal structures of two papain-like cysteine proteases ervatamin-A and ervatamin-C,
complexed with an irreversible inhibitor, together with enzyme kinetics and molecular