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Atomic-resolution structures of type I ribosome inactivating protein alpha-momorcharin with different substrate

Xiaojiao Fan1, Yang Wang2, Feng Guo2

  • 1Department of Obstetrics and Gynecology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China; Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, CAS Center for Excellence in Molecular Cell Science, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui, China.

International Journal of Biological Macromolecules
|July 13, 2020
PubMed

Insights

Alpha-momorcharin (Alpha-MMC), a ribosome inactivating protein, binds to adenine and guanine analogs. Structural insights into Alpha-MMC

Area of Science:

  • Biochemistry
  • Structural Biology
  • Molecular Biology

Background:

  • Alpha-momorcharin (Alpha-MMC) is a type I ribosome inactivating protein (RIP) derived from bitter melon seeds.
  • Alpha-MMC functions by cleaving adenine from 28S rRNA, thereby inhibiting protein biosynthesis.

Purpose of the Study:

  • To elucidate the substrate binding mechanisms of Alpha-MMC.
  • To provide structural insights into the enzymatic activity of Alpha-MMC.
  • To lay the groundwork for developing Alpha-MMC poisoning inhibitors.

Main Methods:

  • X-ray crystallography was employed to determine seven crystal complex structures of Alpha-MMC.
  • Structures were resolved at high resolution, ranging from 1.08 Å to 1.52 Å.
  • Complexes were formed with various substrate analogs including adenine, AMP, cAMP, dAMP, ADP, GMP, and xanthosine.

Main Results:

  • The crystal structures reveal that Alpha-MMC effectively binds to both adenine and guanine analogs.
  • The side chain of tyrosine 93 (Tyr93) was observed in two conformations, acting as a gate for the substrate binding pocket.
  • While the binding site is conserved among RIPs, specific interacting residues differ between Alpha-MMC and other RIPs.

Conclusions:

  • The study provides detailed structural information on Alpha-MMC's interaction with diverse substrate analogs.
  • Understanding these enzymatic mechanisms is crucial for Alpha-MMC research.
  • These findings may facilitate the design of novel therapeutic agents against Alpha-MMC toxicity.
Keywords:
Alpha-momorcharinRibosome-inactivating proteinSubstrate analogs

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