title: High precision NMR structure and function of the RING-H2 finger domain of EL5, a rice protein whose expression is increased upon exposure to pathogen-derived oligosaccharides.
abstract: EL5, a RING-H2 finger protein, is rapidly induced by N-acetylchitooligosaccharides in rice cell. We expressed the EL5 RING-H2 finger domain in Escherichia coli and determined its structure in solution by NMR spectroscopy. The EL5 RING-H2 finger domain consists of two-stranded beta-sheets (beta1, Ala(147)-Phe(149); beta2, Gly(156)-His(158)), one alpha-helix (Cys(161)-Leu(166)), and two large N- and C-terminal loops. It is stabilized by two tetrahedrally coordinated zinc ions. This structure is similar to that of other RING finger domains of proteins of known function. From structural analogies, we inferred that the EL5 RING-H2 finger is a binding domain for ubiquitin-conjugating enzyme (E2). The binding site is probably formed by solvent-exposed hydrophobic residues of the N- and C-terminal loops and the alpha-helix. We demonstrated that the fusion protein with EL5-(96-181) and maltose-binding protein (MBP) was polyubiquitinated by incubation with ubiquitin, ubiquitin-activating enzyme (E1), and a rice E2 protein, OsUBC5b. This supported the idea that the EL5 RING finger domain is essential for ubiquitin-ligase activity of EL5. By NMR titration experiments, we identified residues that are critical for the interaction between the EL5 RING-H2 finger and OsUBC5b. We conclude that the RING-H2 finger domain of EL5 is the E2 binding site of EL5.
authors.affiliation: Biochemistry Department, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan.
authors.forename: Shizue
authors.initials: S
authors.lastname: Katoh
authors.forename: Cui
authors.initials: C
authors.lastname: Hong
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tsunoda
authors.forename: Katsuyoshi
authors.initials: K
authors.lastname: Murata
authors.forename: Ryota
authors.initials: R
authors.lastname: Takai
authors.forename: Eiichi
authors.initials: E
authors.lastname: Minami
authors.forename: Toshimasa
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Etsuko
authors.initials: E
authors.lastname: Katoh
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism; D008025:Ligases / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012275:Oryza / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry; D011135:Polysaccharides, Bacterial / Q000494:pharmacology; D011487:Protein Conformation; D025801:Ubiquitin / Q000378:metabolism; D044764:Ubiquitin-Activating Enzymes; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases; D016335:Zinc Fingers
chemical_list: D002352:Carrier Proteins; D010940:Plant Proteins; D011135:Polysaccharides, Bacterial; D025801:Ubiquitin; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; D044764:Ubiquitin-Activating Enzymes