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Start Over Descriptor "N-Glycosyl Hydrolases classification" Topic plant proteins
2 results on '"N-Glycosyl Hydrolases classification"'

1. Evidence for the importance of electrostatics in the function of two distinct families of ribosome inactivating toxins.

Author

Korennykh AV, Correll CC, and Piccirilli JA

Subjects
Endoribonucleases physiology, Fungal Proteins physiology, N-Glycosyl Hydrolases classification, Plant Proteins classification, Protein Synthesis Inhibitors pharmacology, Ribosome Inactivating Proteins, Type 1, Ribosomes chemistry, Ricin classification, Ricin pharmacology, Saporins, Static Electricity, Sulfuric Acid Esters classification, Sulfuric Acid Esters pharmacology, Surface Properties, Triterpenes classification, Triterpenes pharmacology, Endoribonucleases chemistry, Fungal Proteins chemistry, Multigene Family physiology, N-Glycosyl Hydrolases chemistry, N-Glycosyl Hydrolases physiology, Plant Proteins chemistry, Plant Proteins physiology, Protein Synthesis Inhibitors chemistry, Ribosomes metabolism, Ricin chemistry, Sulfuric Acid Esters chemistry, Triterpenes chemistry
Abstract

Alpha-sarcin and ricin represent two structurally and mechanistically distinct families of site-specific enzymes that block translation by irreversibly modifying the sarcin/ricin loop (SRL) of 23S-28S rRNA. alpha-Sarcin family enzymes are designated as ribotoxins and act as endonucleases. Ricin family enzymes are designated as ribosome inactivating proteins (RIP) and act as N-glycosidases. Recently, we demonstrated that basic surface residues of the ribotoxin restrictocin promote rapid and specific ribosome targeting by this endonuclease. Here, we report that three RIP: ricin A, saporin, and gypsophilin depurinate the ribosome with strong salt sensitivity and achieve unusually fast kcat/Km approximately 10(9)-10(10) M(-1) s(-1), implying that RIP share with ribotoxins a common mechanism of electrostatically facilitated ribosome targeting. Bioinformatics analysis of RIP revealed that surface charge properties correlate with the presence of the transport chain in the RIP molecule, suggesting a second role for the surface charge in RIP transport. These findings put forward surface electrostatics as an important determinant of RIP activity.

Published
2007
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2. Iris bulbs express type 1 and type 2 ribosome-inactivating proteins with unusual properties.

Author

Hao Q, Van Damme EJ, Hause B, Barre A, Chen Y, Rougé P, and Peumans WJ

Subjects
Amino Acid Sequence, Lectins chemistry, Lectins classification, Models, Molecular, Molecular Sequence Data, N-Glycosyl Hydrolases chemistry, N-Glycosyl Hydrolases classification, Phylogeny, Plant Proteins chemistry, Plant Proteins classification, Protein Conformation, Sequence Alignment, Sequence Homology, Amino Acid, Iris Plant metabolism, Lectins metabolism, N-Glycosyl Hydrolases metabolism, Plant Proteins metabolism, Plant Roots metabolism, Ribosomes genetics
Abstract

Two closely related lectins from bulbs of the Dutch iris (Iris hollandica var. Professor Blaauw) have been isolated and cloned. Both lectins, called Iris agglutinin b and Iris agglutinin r, possess N-glycosidase activity and share a high sequence similarity with previously described type 2 ribosome-inactivating proteins (RIP). However, these lectins show only 57% to 59% sequence identity to a previously characterized type 1 RIP from iris, called IRIP. The identification of the iris lectins as type 2 RIP provides unequivocal evidence for the simultaneous occurrence of type 1 and type 2 RIP in iris bulbs and allowed a detailed comparison of type 1 and type 2 RIP from a single plant, which provides further insight into the molecular evolution of RIP. Binding studies and docking experiments revealed that the lectins exhibit binding activity not only toward Gal/N-acetylgalactosamine, but also toward mannose, demonstrating for the first time that RIP-binding sites can accommodate mannose.

Published
2001
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