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Ligand-Induced Conformational Changes near the Active Site Regulating Enzyme Activity of Momorcharins from Seeds of Bitter Gourd

Authors
  • Matsunaga, Chie1
  • Okada, Yuuki1
  • Nishimoto, Etsuko1
  • 1 Graduate School of Kyushu University, Laboratory of Biophysical Chemistry, Faculty of Agriculture, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan , Fukuoka (Japan)
Type
Published Article
Journal
Journal of Fluorescence
Publisher
Springer-Verlag
Publication Date
Dec 19, 2018
Volume
29
Issue
1
Pages
231–240
Identifiers
DOI: 10.1007/s10895-018-2332-2
Source
Springer Nature
Keywords
License
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Abstract

It is reasonable to consider that Type I-ribosomal inactivation proteins (RIP) retain some specific affinity to harmful pathogens to complete the role as a bio-defense relating protein. In the present studies, it was shown that two Type I-RIPs, α- and β-momorcharins, maintained the abilities to bind with N-acetylglucosamine (NAG) to change the conformation around the active sites and to regulate their N-glycosidase activities. By the binding of NAG, the freedom of internal motion of Trp192 in α-momorcharin was increased 1.5 times near the active site and, on the other hand, the corresponding motion of Trp190 was limited 50% in β-momorcharin. The results in the fluorescence resonance excitation energy transfer experiments demonstrated that Trp-190 of β-momorcharin was kept away from Tyr-70 but Trp192 contrarily approached closer to the nearest neighboring Tyr residue consisting of the active center of α-momorcharin by the binding with NAG. These conformational changes near the active site close correlated with promotion and/or suppression of the N-glucosidase activities of β- and α-momorcharins.

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