@article { ISI:000315370000010, title = {Polyproline fold-In imparting kinetic stability to an alkaline serine endopeptidase}, journal = {Biochimica Et Biophysica Acta-Proteins and Proteomics}, volume = {1834}, number = {3}, year = {2013}, month = {MAR}, pages = {708-716}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Polyproline II (PPII) fold, an unusual structural element was detected in the serine protease from Nocardiopsis sp. NCIM 5124 (NprotI) based on far UV circular dichroism spectrum, structural transitions of the enzyme in presence of GdnHCl and a distinct isodichroic point in chemical and thermal denaturation. The functional activity and conformational transitions of the enzyme were studied under various denaturing conditions. Enzymatic activity of NprotI was stable in the vicinity of GdnHCl upto 6.0 M concentration, organic solvents viz, methanol, ethanol, propanol (all 90\% v/v), acetonitrile (75\% v/v) and proteases such as trypsin, chymottypsin and proteinase K (NprotI:protease 10:1). NprotI seems to be a kinetically stable protease with a high energy barrier between folded and unfolded states. Also, an enhancement in the activity of the enzyme was observed in 1 M GdnHCl upto 8 h, in organic solvents (75\% v/v) for 72 h and in presence of proteolytic enzymes. The polyproline fold remained unaltered or became more prominent under the above mentioned conditions. However, it diminished gradually during thermal denaturation above 60 degrees C. Thermal transition studies by differential scanning calorimetry (DSC) showed scan rate dependence as well as irreversibility of denaturation, the properties characteristic of kinetically stable proteins. This is the first report of PPII helix being the global conformation of a non structural protein, an alkaline serine protease, from a microbial source, imparting kinetic stability to the protein. (C) 2013 Elsevier B.V. All rights reserved.

}, keywords = {Conformation, differential scanning calorimetry, Kinetic stability, Nocardiopsis sp., Polyproline fold, Serine protease}, issn = {1570-9639}, doi = {10.1016/j.bbapap.2012.12.007}, author = {Rohamare, Sonali B. and Dixit, Vaishali and Nareddy, Pavan Kumar and Sivaramakrishna, D. and Swamy, Musti J. and Gaikwad, Sushama M.} } @article { ISI:000334147300006, title = {Conformational transitions of cinnamoyl CoA reductase 1 from leucaena leucocephala}, journal = {International Journal of Biological Macromolecules }, volume = {64}, year = {2014}, month = {MAR}, pages = {30-35}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Conformational transitions of cinnamoyl CoA reductase, a key regulatory enzyme in lignin biosynthesis, from Leucaena leucocephala (L1-CCRH1) were studied using fluorescence and circular dichroism spectroscopy. The native protein possesses four trp residues exposed on the surface and 66\% of helical structure, undergoes rapid structural transitions at and above 45 C and starts forming aggregates at 55 C. LI-CCRH1 was transformed into acid induced (pH 2.0) molten globule like structure, exhibiting altered secondary structure, diminished tertiary structure and exposed hydrophobic residues. The molten globule like structure was examined for the thermal and chemical stability. The altered secondary structure of Ll -CCRH1 at pH 2.0 was stable up to 90 C. Also, in presence of 0.25 M guanidine hydrochloride (GdnHCI), it got transformed into different structure which was stable in the vicinity of 2 M GdnHCI (as compared to drastic loss of native structure in 2 M GdnHC1) as seen in far UV-CD spectra. The structural transition of LI-CCRH1 at pH 2.0 followed another transition after readjusting the pH to 8.0, forming a structure with hardly any similarity to that of native protein. (C) 2013 Elsevier B.V. All rights reserved.

}, keywords = {Aggregation Cinnamoyl CoA reductase, Conformation, Molten globule, Thermostability, Unfolding}, issn = {0141-8130}, doi = {10.1016/j.ijbiomac.2013.11.024}, author = {Sonawane, Prashant D. and Khan, Bashir Mohammad and Gaikwad, Sushama M.} } @article {45551, title = {Investigation of structural and saccharide binding transitions of Bauhinia purpurea and Wisteria floribunda lectins}, journal = {Archives of Biochemistry and Biophysics}, volume = {662}, year = {2019}, month = {FEB }, pages = {134-142}, type = {Article}, abstract = {

Two novel medicinally important legume lectins from Bauhinia purpurea (BPL) and Wisteria floribunda (WFL) possessing extended sugar binding site were investigated for functional and conformational transitions using biochemical and biophysical techniques as well as bioinformatical tools. Homology model of BPL was constructed using the Schrodinger suite and docked with N-acetyl galactosamine and T-antigen disaccharide (Gal beta 1-3GalNAc alpha O-Me). The longer loop D in the structure of WFL compared to that in BPL was found to be responsible for its specificity to LacdiNac (beta-D-GalNAc-[1 -\> 4]-DGlcNAc) over Gal beta 1-3GalNAc. BPL remained functionally stable up to 40 degrees C whereas WFL remained stable upto 70 degrees C indicating the strength of the sugar binding site geometry. Both the lectins showed intense but non-specific secondary structure in the range of 65-90 degrees C. WFL showed rapid aggregation above 80 degrees C as indicated by light scattering intensity. The lectins showed simultaneous dissociation and multistate unfolding in the vicinity of GdnHCl. At pH 1.0, both the lectins exhibited molten globule like structures, which were characterized further and were found to respond in a different way towards denaturants. The results have provided valuable insights into the molecular basis of the activity and stability of the two lectins.

}, keywords = {Conformation, Homology model, Lectin, Molten globule, saccharide binding, Thermal aggregation}, issn = {0003-9861}, doi = {10.1016/j.abb.2018.12.003}, author = {Agrawal, Sanskruthi B. and Ghosh, Deepanjan and Gaikwad, Sushama M.} }