@article { ISI:000291061500032, title = {Conformational transitions in ariesaema curvatum lectin: characterization of an acid induced active molten globule}, journal = {Journal of Fluorescence}, volume = {21}, number = {2}, year = {2011}, month = {MAR}, pages = {753-763}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Biophysical characterization of a lectin from Ariesaema curvatum (ACL) was carried out using steady state as well as time resolved fluorescence and CD spectroscopy under various denaturing conditions. An intermediate with altered tryptophan microenvironment was detected in the phase diagram, which exibited pronounced secondary structure and hemagglutinating activity in presence of 0.25 M Gdn-HCl. An acid induced molten- globule like structure possessing activity and higher thermostability was detected. Transition to the molten globule state was reversible in nature. The lectin retained hemagglutinating activity even after incubation at 95 A degrees C. Both chemical and thermal unfolding of the lectin were found to consist of multistate processes. Fluorescence quenching of ACL was strong with acrylamide and KI. The single tryptophan was found to be surrounded by high density of the positively charged amino acid residues as shown by a ten fold higher K(sv) for KI compared to that for CsCl. The average lifetime of tryptophan fluorescence increased from 1.24 ns in the native state to 1.72 ns in the denatured state.

}, keywords = {Araceae, Fluorescence lifetime, Hemagglutinin, Molten globule, Secondary structure, Thermostability, Unfolding}, issn = {1053-0509}, doi = {10.1007/s10895-010-0766-2}, author = {Sharma, Urvashi and Gaikwad, Sushama M. and Suresh, C. G. and Dhuna, Vikram and Singh, Jatinder and Kamboj, Sukhdev Singh} } @article { ISI:000301921300006, title = {Crystallization and X-ray structure analysis of a thermostable penicillin G acylase from alcaligenes faecalis}, journal = {Acta Crystallographica Section F-Structural Biology and Crystallization Communications}, volume = {68}, number = {3}, year = {2012}, month = {MAR}, pages = {273-277}, publisher = {WILEY-BLACKWELL}, address = {COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA}, abstract = {

{The enzyme penicillin G acylase (EC 3.5.1.11) catalyzes amide-bond cleavage in benzylpenicillin (penicillin G) to yield 6-aminopenicillanic acid, an intermediate chemical used in the production of semisynthetic penicillins. A thermostable penicillin G acylase from Alcaligenes faecalis (AfPGA) has been crystallized using the hanging-drop vapour-diffusion method in two different space groups: C2221, with unit-cell parameters a = 72.9

}, keywords = {calcium binding, disulfide bridges, Ntn hydrolases, orthorhombic form, tetragonal form, Thermostability}, issn = {1744-3091}, doi = {10.1107/S1744309111053930}, author = {Varshney, Nishant Kumar and Kumar, R. Suresh and Ignatova, Zoya and Prabhune, Asmita and Pundle, Archana and Dodson, Eleanor J. and Suresh, C. G.} } @article { ISI:000362964900007, title = {Sequence and structure-based comparative analysis to assess, identify and improve the thermostability of penicillin G acylases}, journal = {Journal of Industrial Microbiology \& Biotechnology}, volume = {42}, number = {11}, year = {2015}, month = {NOV}, pages = {1493-1506}, publisher = {SPRINGER HEIDELBERG}, address = {TIERGARTENSTRASSE 17, D-69121 HEIDELBERG, GERMANY}, abstract = {

Penicillin acylases are enzymes employed by the pharmaceutical industry for the manufacture of semi-synthetic penicillins. There is a continuous demand for thermostable and alkalophilic enzymes in such applications. We have carried out a computational analysis of known penicillin G acylases (PGAs) in terms of their thermostable nature using various protein-stabilizing factors. While the presence of disulfide bridges was considered initially to screen putative thermostable PGAs from the database, various other factors such as high arginine to lysine ratio, less content of thermolabile amino acids, presence of proline in beta-turns, more number of ion-pair and other non-bonded interactions were also considered for comparison. A modified consensus approach designed could further identify stabilizing residue positions by site-specific comparison between mesostable and thermostable PGAs. A most likely thermostable enzyme identified from the analysis was PGA from Paracoccus denitrificans (PdPGA). This was cloned, expressed and tested for its thermostable nature using biochemical and biophysical experiments. The consensus site-specific sequence-based approach predicted PdPGA to be more thermostable than Escherichia coli PGA, but not as thermostable as the PGA from Achromobacter xylosoxidans. Experimental data showed that PdPGA was comparatively less thermostable than Achromobacter xylosoxidans PGA, although thermostability factors favored a much higher stability. Despite being mesostable, PdPGA being active and stable at alkaline pH is an advantage. Finally, several residue positions could be identified in PdPGA, which upon mutation selectively could improve the thermostability of the enzyme.

}, keywords = {Alkalistable, beta-lactam antibiotics, Consensus approach, Disulfide bridge, Ion pairs, Penicillin acylase, Thermostability}, issn = {1367-5435}, doi = {10.1007/s10295-015-1690-x}, author = {Panigrahi, Priyabrata and Chand, Deepak and Mukherji, Ruchira and Ramasamy, Sureshkumar and Suresh, C. G.} }