the critical role of n- and c-terminal contact in protein stability and folding of a family 10 xylanase under extreme conditionsn - c端接触的关键作用蛋白质稳定性和折叠的家庭10在极端条件下木聚糖酶.pdf

The Critical Role of N- and C-Terminal Contact in Protein Stability and Folding of a Family 10 Xylanase under Extreme Conditions 1,2 1 2 3 Amit Bhardwaj , Sadhu Leelavathi , Sudeshna Mazumdar-Leighton , Amit Ghosh , Suryanarayanarao 4,5 1 Ramakumar , Vanga S. Reddy * 1 International Centre for Genetic Engineering and Biotechnology, New Delhi, India, 2 Department of Botany, University of Delhi, Delhi, India, 3 National Institute of Cholera and Enteric Diseases, Kolkata, India, 4 Department of Physics, Indian Institute of Science, Bangalore, India, 5 Bioinformatics Centre, Indian Institute of Science, Bangalore, India Abstract Background: Stabilization strategies adopted by proteins under extreme conditions are very complex and involve various kinds of interactions. Recent studies have shown that a large proportion of proteins have their N- and C-terminal elements in close contact and suggested they play a role in protein folding and stability. However, the biological significance of this contact remains elusive. Methodology: In the present study, we investigate the role of N- and C-terminal residue interaction using a family 10 xylanase (BSX) with a TIM-barrel structure that shows stability under high temperature, alkali pH, and protease and SDS treatment. Based on crystal structure, an aromatic cluster was identified that involves Phe4, Trp6 and Tyr343 holding the N- and C-terminus together; this is a unique and important feature of this protein that might be crucial for folding and stability under poly-extreme conditions. Conclusion: A series of mutants was created to disrupt this aromatic cluster formation and study the loss of stability and function u