@article { ISI:000237610600013, title = {Purification, characterization and substrate specificity of thermostable alpha-galactosidase from Bacillus stearothermophilus (NCIM-5146)}, journal = {Process Biochemistry}, volume = {41}, number = {6}, year = {2006}, month = {JUN}, pages = {1311-1317}, publisher = {ELSEVIER SCI LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

An extracellular thermostable alpha-galactosidase from Bacillus stearothermophilus (NCIM-5146) has been purified to homogeneity by chromatographic step, using Phenyl Sepharose CL-4B column. The specific activity of the enzyme was increased approximately 389-fold, from 1.03 U/mg protein to 400 U/mg protein. The molecular mass of the purified enzyme as determined by SDS-PAGE and gel filtration was 79.9 and 165.9 kDa, respectively, suggesting dimeric nature. The purified alpha-galactosidase is a non-glycosylated protein with a pI of 4.9. The pH and temperature optima for the purified enzyme are 6.5-7.0 and 65 degrees C, respectively. The alpha-galactosidase is stable over a broad pH range (3-9) and its half-life of inactivation (t(1/2)) at 70 degrees C is 30 min. The partial N-terminal sequence of alpha-galactosidase showed remarkable homology (80\% similarity) with earlier reported alpha-galactosidase from B. stearothermophilus NUB 3621. The secondary structure of the enzyme determined by circular dichroism (CD) spectroscopy exhibited alpha/beta class of protein and showed temperature induced conformational forms below and above the transition temperature. The purified enzyme showed biphasic Arrhenius plot with break point at 55 degrees C for pNPG and 50 degrees C for melibiose, raffinose and stachyose. The enzyme hydrolyzes alpha-1-3, alpha-1-4, and alpha-1-6 galactosidic linkages and not the beta-galactosidic linkages. Synthetic substrates pNPG and oNPG had lower K-m and higher K-cat as compare to natural substrates, melibiose, raffinose, and stachyose. (c) 2006 Elsevier Ltd. All rights reserved.

}, keywords = {alpha-galactosidase, Bacillus stearothermophilus (NCIM-5146), Purification, Secondary structure, thermostable enzyme}, issn = {1359-5113}, doi = {10.1016/j.procbio.2006.01.003}, author = {Gote, M. M. and Khan, Mohammad Islam and Gokhale, D. V. and Bastawade, Kulbhushan B. and Khire, Jayant Malhar} } @article { ISI:000253563900018, title = {Structure-activity relationship of a hemagglutinin from Moringa oleifera seeds}, journal = {International Journal of Biological Macromolecules}, volume = {42}, number = {2}, year = {2008}, month = {MAR}, pages = {203-207}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The hemagglutinin from the seeds of Moringa oleifera (MoL) agglutinates human as well as rabbit erythrocytes; the affinity for the latter is almost 250 times more than that for the former. MoL was inhibited by glycoproteins namely thyroglobulin, fetuin and holotransferin indicating the complex sugar specificity of the lectin. The protein is a homodimer with molecular mass of 14 kDa, subunits (7.1 kDa) linked by the disulfide bond(s). The secondary structure elements of MoL area-helix, 28\%; beta-sheet, 23\%; turn 20\% and unordered 28\%. While the activity and secondary structure were not affected at extreme pH and high temperature, they were drastically affected in presence of dithiothreitol at and above pH 7.0, indicating that disulfide linkages hold the active conformation of the protein. (C) 2007 Elsevier B.V. All rights reserved.

}, keywords = {disulfide linkages, Moringa oleifera hemagglutinin, Secondary structure}, issn = {0141-8130}, doi = {10.1016/j.ijbiomac.2007.10.024}, author = {Katre, Uma V. and Suresh, C. G. and Khan, Mohammad Islam and Gaikwad, Sushama M.} } @article { ISI:000264484400007, title = {Comparative studies of two araceous lectins by steady state and time-resolved fluorescence and CD spectroscopy}, journal = {Journal of Fluorescence}, volume = {19}, number = {2}, year = {2009}, month = {MAR}, pages = {239-248}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Transitions in the tryptophan microenvironment and secondary structure of two monocot lectins from Sauromatum guttatum and Arisaema tortuosum under different denaturing conditions were studied by steady state and time resolved fluorescence and CD spectroscopy. The lectins exist as tetramers with a single tryptophan residue estimated per monomer, present in a polar environment. Quenching with ionic quenchers showed predominantly electropositive environment for tryptophan residues. Acrylamide had maximum quenching effect. A decrease in KI quenching due to lectin denaturation indicated redistribution of charges as a result of possible conformational change. The two values for lifetimes of tryptophanyl population (1.2-1.4 and 6.3-6.4 ns) reduced substantially on quenching or denaturation. Similarly, both the lectins showed a drastic loss of secondary structure in 5 M Gdn-HCl or 6 M Urea or at pH 2.0 and below. For the first time araceous lectins, like legume lectins are shown to bind adenine. The presence of a compact structure at alkaline pH 10.0-12.0 was observed in CD spectra.

}, keywords = {Araceae lectins, Denaturation, fluorescence, Lifetime spectroscopy, Secondary structure}, issn = {1053-0509}, doi = {10.1007/s10895-008-0409-z}, author = {Dharker, Poorva N. and Gaikwad, Sushama M. and Suresh, C. G. and Dhuna, Vikram and Khan, Mohammad Islam and Singh, Jatinder and Kamboj, Sukhdev Singh} } @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 {44651, title = {Cloning and characterization of trehalase: a conserved glycosidase from oriental midge, Chironomus ramosus}, journal = {3 Biotech}, volume = {8}, year = {2018}, month = {AUG}, pages = {352}, abstract = {

Insect trehalase is a multiferous enzyme, crucial for normal physiological functions as well as under stress conditions. In this report, we present a fundamental study of the trehalase gene segment (1587 bp) from Chironomus ramosus (CrTre) encoding for 529 amino acids, using appropriate bioinformatics tools. C. ramosus, a tropical midge is an emerging animal model to investigate the consequences of environmental stresses. We observed that CrTre belongs to GH family 37 in the CAZy database and possess 57-92\% identity to dipteran trehalases. In silico characterization provided information regarding the structural, functional and evolutionary aspects of midge trehalase. In the phylogenetic tree, CrTre clustered with the soluble dipteran trehalases. Moreover, domain functional characterization of the deduced protein sequence by InterProScan (IPR001661), ProSite (PS00927 and PS00928) and Pfam (PF01204) indicated presence of highly conserved signature motifs which are important for the identification of trehalase superfamily. Furthermore, the instability index of CrTre was predicted to be \< 40 suggesting its in vivo stability while, the high aliphatic index indicated towards its thermal stability (index value 71-81). The modelled 3D tertiary structure of CrTre depicts a (alpha/alpha)(6) barrel toroidal core. The catalytic domain of the enzyme comprised Glu424 and Asp226 as the putative active site residues. Interestingly, the conserved motifs were observed to be formed by the flexible loopy regions in the tertiary structure. This study revealed essential sequence features of the midge trehalase and offers better insights into the structural aspects of this enzyme which can be correlated with its function.

}, keywords = {Conserved motifs, Homology modelling, Midges, Secondary structure, trehalose}, issn = {2190-572X}, doi = {10.1007/s13205-018-1376-y}, author = {Shukla, Ekta and Thorat, Leena and Bendre, Ameya D. and Jadhav, Santosh and Pal, Jayanta K. and Nath, Bimalendu B. and Gaikwad, Sushama M.} } @article {46174, title = {Secondary structure of the internal transcribed rDNA (ITS) regions of cosmopolites sordidus (Germar) and odoiporus longicollis (Olivier): a first report in family Curculionidae}, journal = {International Journal of Tropical Insect Science}, volume = {39}, year = {2019}, month = {MAR}, pages = {53-61}, type = {Article}, abstract = {

In the present work the consensus secondary structure of the internal transcribed rDNA spacers ITS1 and ITS2 of two weevils i.e. Cosmopolites sordidus (Germar) and Odoiporus longicollis (Olivier) has been described. The secondary structures of the ITS1 region of C.sordidus and O.longicollis have ten and five helices respectively, emerging from a central core. Two and five helices emerge from a central core in the ITS2 secondary structures of C.sordidus and O.longicollis respectively, and do not conform to the {\textquoteleft}paneukaryotic{\textquoteright} four domain model. The ITS2 sequences of these two weevils share three regions with maximum sequence identity. Of these, two are present at the 5{\textquoteright} and 3{\textquoteright} end and share structural similarity, suggesting their possible role in the processing of the rRNA. This is the first report of the secondary structure of the ITS region in family Curculionidae which can serve as a valuable resource for homology modelling and phylogenetic studies.

}, keywords = {Cosmopolites sordidus (Germar), Curculionidae, ITS1, ITS2, Odoiporus longicollis (Olivier), Secondary structure}, issn = {1742-7584}, doi = {10.1007/s42690-019-00016-7}, author = {Kumar, Lalitha Sunil} }