EL5, a rice N-acetylchitooligosaccharide elicitor-responsive RING-H2 finger protein, is a ubiquitin ligase which functions in vitro in co-operation with an elicitor-responsive ubiquitin-conjugating enzyme, OsUBC5b.
EL5, a rice gene responsive to N-acetylchitooligosaccharide elicitor, encodes a RING-H2 finger protein with structural features common to the plant-specific ATL family. We show that the fusion protein of EL5 with maltose binding protein (MBP) was polyubiquitinated by incubation with ubiquitin, ubiquitin-activating enzyme (E1), and the Ubc4/5 subfamily of the ubiquitin-conjugating enzyme (E2). EL5 possesses the activity to catalyse the transfer of ubiquitin to the MBP moiety, and the RING-H2 finger motif of EL5 is necessary for this activity. Thus, we concluded that EL5 represents a ubiquitin ligase (E3). We also show that two rice E2s (OsUBC5a, OsUBC5b) of the Ubc4/5 subfamily function as E2 which catalyses EL5-mediated ubiquitination, and OsUBC5b was induced by elicitor, as well as EL5. These results strongly suggest that EL5 and OsUBC5b have roles in plant defense response through the turnover of protein(s) via the ubiquitin/proteasome system.
Takai
Ryota
R
Institute of Applied Biochemistry, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8572, Japan.
Matsuda
Noriyuki
N
Nakano
Akihiko
A
Hasegawa
Koji
K
Akimoto
Chiharu
C
Shibuya
Naoto
N
Minami
Eiichi
E
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D003001:Cloning, Molecular; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008025:Ligases / Q000235:genetics* / Q000378:metabolism; D058619:Maltose-Binding Proteins; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000378:metabolism / Q000494:pharmacology; D012275:Oryza / Q000187:drug effects / Q000235:genetics* / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D044763:Ubiquitin-Conjugating Enzymes; D014452:Ubiquitins / Q000378:metabolism / Q000494:pharmacology; D016335:Zinc Fingers / Q000235:genetics*
D002352:Carrier Proteins; D007527:Isoenzymes; D058619:Maltose-Binding Proteins; D009844:Oligosaccharides; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D014452:Ubiquitins; D044763:Ubiquitin-Conjugating Enzymes; C063109:ubiquitin-conjugating enzyme UBC4; D008025:Ligases