Lee BG, Kim MK, Kim BW, Suh SW, Song HK. Structures of the ribosome-inactivating protein from barley seeds reveal a unique activation mechanism.
ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2012;
68:1488-500. [PMID:
23090398 DOI:
10.1107/s0907444912037110]
[Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Accepted: 08/28/2012] [Indexed: 05/26/2023]
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.
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