title: Structures of the ribosome-inactivating protein from barley seeds reveal a unique activation mechanism.
abstract: Ribosome-inactivating protein (RIP), a defence protein found in various plants, possesses different chain architectures and activation mechanisms. The RIP from barley (bRIP) is a type I RIP and has sequence features that are divergent from those of type I and type II RIPs from dicotyledonous plants and even the type III RIP from maize. This study presents the first crystal structure of an RIP from a cereal crop, barley, in free, AMP-bound and adenine-bound states. For phasing, a codon-optimized synthetic brip1 gene was used and a vector was constructed to overexpress soluble bRIP fusion proteins; such expression has been verified in a number of cases. The overall structure of bRIP shows folding similar to that observed in other RIPs but also shows significant differences in specific regions, particularly in a switch region that undergoes a structural transition between a 3(10)-helix and a loop depending on the liganded state. The switch region is in a position equivalent to that of a proteolytically susceptible and putative ribosome-binding site in type III RIPs. Thus, the bRIP structure confirms the detailed enzymatic mechanism of this N-glycosidase and reveals a novel activation mechanism for type I RIPs from cereal crops.
authors.affiliation: School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea.
authors.forename: Byung-Gil
authors.initials: BG
authors.lastname: Lee
authors.forename: Min Kyung
authors.initials: MK
authors.lastname: Kim
authors.forename: Byeong-Won
authors.initials: BW
authors.lastname: Kim
authors.forename: Se Won
authors.initials: SW
authors.lastname: Suh
authors.forename: Hyun Kyu
authors.initials: HK
authors.lastname: Song
mesh_terms: D000225:Adenine / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics; D001467:Hordeum / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D054788:Ribosome Inactivating Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012639:Seeds / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D040681:Structural Homology, Protein; D015854:Up-Regulation
chemical_list: D011993:Recombinant Fusion Proteins; D000249:Adenosine Monophosphate; D054788:Ribosome Inactivating Proteins; D000225:Adenine