Conformational Transitions in <Emphasis Type="Italic">Ariesaema curvatum</Emphasis> Lectin: Characterization of an Acid Induced Active Molten Globule |
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Authors: | Urvashi Sharma Sushama M Gaikwad C G Suresh Vikram Dhuna Jatinder Singh Sukhdev Singh Kamboj |
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Institution: | (1) Division of Biochemical Sciences, National Chemical Laboratory, Pune, Maharashtra, 411008, India;(2) Department of Molecular Biology and Biochemistry, Guru Nanak Dev University, Amritsar, 143005, Punjab, India; |
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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 °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 Ksv 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. |
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