Journal of Biochemistry Advance Access originally published online on May 26, 2009
Journal of Biochemistry 2009 146(3):343-350; doi:10.1093/jb/mvp076
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Fatty Acids Bound to Recombinant Tear Lipocalin and Their Role in Structural Stabilization
Department of Bioinformatics, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan
*To whom correspondence should be addressed. Tel: +81-42-691-9444, Fax: +81-42-691-9312, E-mail: ikeguchi{at}soka.ac.jp
Received October 27, 2008; Accepted May 8, 2009
| Abstract |
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A variant of human tear lipocalin was expressed in Escherichia coli, and the bound fatty acids were analysed by gas chromatography, mass spectroscopy and nuclear magnetic resonance spectroscopy. Five major fatty acids were identified as hexadecanoic acid (palmitic acid, PA), cis-9-hexadecenoic acid (palmitoleic acid), 9,10-methylenehexadecanoic acid, cis-11-octadecenoic acid (vaccenic acid) and 11,12-methyleneoctadecanoic acid (lactobacillic acid). The composition of the bound fatty acids was similar to the fatty acid composition of E. coli extract, suggesting that the binding affinities are similar for these fatty acids. The urea-induced and thermal-unfolding transitions of the holoprotein (nondelipidated), apoprotein (delipidated) and PA-bound protein were observed by circular dichroism. Holoproteins and PA-bound proteins showed the same stability against urea and heat, and were more stable than apoprotein. These results show that each bound fatty acid stabilizes recombinant tear lipocalin to a similar extent.
Key Words: cyclopropane fatty acid, Escherichia coli, expression, urea, unfolding
Abbreviations: HTL, human tear lipocalin; PA, palmitic acid; WT, wild type