title: Factors affecting activation of the 'cloaked' Zea maize ribosome inactivating protein (RIP) zymogen. 1. 'LID' peptide hydrophobicities and oxidative structural changes.
abstract: We want to understand how environmental factors influence zymogen activation of the "cloaked' active site of the 'Ribosome Inactivating Protein' (RIP) from corn kernels. In this study, we focus on how likely chemical effectors in the immediate environment of the 'lid' conspire to unleash the active site upon encountering target membranes of invading pests. Octanol-H2O partitioning free energies of peptides which (i) straddle the proteolysis site, and (ii) form the 'side' and 'bottom' of the proposed 'lid' were found to only slightly favor H2O, suggesting that the peptide is poised to detach from the less polar surface surrounding the RIP active site. Circular dichroism results obtained upon catalase/H2O2 oxidation of the 'lid' peptide suggest that the structure shifts from primarily alpha-helical to primarily beta-like. These results suggest that the active site is more easily 'uncloaked' as a result of the lowered solvent polarity conditions and higher oxidant concentrations in the presence of pest membranes encountered during crucial stages of seed germination.
authors.affiliation: Department of Biochemistry, North Carolina State University, Raleigh 27695, USA.
authors.forename: C C
authors.initials: CC
authors.lastname: Hardin
authors.forename: C H
authors.initials: CH
authors.lastname: Lee
authors.forename: D V
authors.initials: DV
authors.lastname: Lieberman
authors.forename: J
authors.initials: J
authors.lastname: Krawetz
authors.forename: S
authors.initials: S
authors.lastname: Jeyarajah
authors.forename: R S
authors.initials: RS
authors.lastname: Boston
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002942:Circular Dichroism; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000737:chemistry* / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009699:N-Glycosyl Hydrolases / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D054788:Ribosome Inactivating Proteins; D012270:Ribosomes / Q000378:metabolism; D003313:Zea mays / Q000378:metabolism
chemical_list: D004792:Enzyme Precursors; D010940:Plant Proteins; D009699:N-Glycosyl Hydrolases; D054788:Ribosome Inactivating Proteins