کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1934436 | 1050640 | 2008 | 5 صفحه PDF | دانلود رایگان |
Heat labile enterotoxin from enterotoxigenic Escherichia coli is similar to cholera toxin (CT) and is a leading cause of diarrhea in developing countries. It consists of an enzymatically active A subunit (LTA) and a carrier pentameric B subunit (LTB). In the current study, we evaluated the importance of the N-terminal region of LTB by mutation analysis. Deletion of the glutamine (ΔQ3) residue and a substitution mutation E7G in the α1 helix region led to defects in LTB protein secretion. Deletion of the proline residue (ΔP2) caused a decrease in α helicity. The ΔP2 mutant affected GM1 ganglioside receptor binding activity without affecting LTB pentamer formation. Upon refolding/reassembly, the ΔP2 mutant showed defective biological activity. The single substitution mutation (E7D) strengthened the helix, imparting structural stability and thereby improved the GM1 ganglioside receptor binding activity. Our results demonstrate the important role of N-terminal α1 helix in maintaining the structural stability and the integrity of GM1 ganglioside receptor binding activity.
Journal: Biochemical and Biophysical Research Communications - Volume 376, Issue 4, 28 November 2008, Pages 770–774