title: Ancient translation factor is essential for tRNA-dependent cysteine biosynthesis in methanogenic archaea.
abstract: Methanogenic archaea lack cysteinyl-tRNA synthetase; they synthesize Cys-tRNA and cysteine in a tRNA-dependent manner. Two enzymes are required: Phosphoseryl-tRNA synthetase (SepRS) forms phosphoseryl-tRNA(Cys) (Sep-tRNA(Cys)), which is converted to Cys-tRNA(Cys) by Sep-tRNA:Cys-tRNA synthase (SepCysS). This represents the ancestral pathway of Cys biosynthesis and coding in archaea. Here we report a translation factor, SepCysE, essential for methanococcal Cys biosynthesis; its deletion in Methanococcus maripaludis causes Cys auxotrophy. SepCysE acts as a scaffold for SepRS and SepCysS to form a stable high-affinity complex for tRNA(Cys) causing a 14-fold increase in the initial rate of Cys-tRNA(Cys) formation. Based on our crystal structure (2.8-Å resolution) of a SepCysS⋅SepCysE complex, a SepRS⋅SepCysE⋅SepCysS structure model suggests that this ternary complex enables substrate channeling of Sep-tRNA(Cys). A phylogenetic analysis suggests coevolution of SepCysE with SepRS and SepCysS in the last universal common ancestral state. Our findings suggest that the tRNA-dependent Cys biosynthesis proceeds in a multienzyme complex without release of the intermediate and this mechanism may have facilitated the addition of Cys to the genetic code.
authors.affiliation: Departments of Molecular Biophysics and Biochemistry and.
authors.forename: Yuchen
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Departments of Molecular Biophysics and Biochemistry andFaculty of Advanced Life Science and.
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Nakamura
authors.affiliation: Graduate School of Life Sciences, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Yuto
authors.initials: Y
authors.lastname: Nakazawa
authors.affiliation: Graduate School of Life Sciences, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Nozomi
authors.initials: N
authors.lastname: Asano
authors.affiliation: Departments of Molecular Biophysics and Biochemistry and.
authors.forename: Kara A
authors.initials: KA
authors.lastname: Ford
authors.affiliation: Departments of Molecular Biophysics and Biochemistry and.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hohn
authors.affiliation: Faculty of Advanced Life Science and.
authors.forename: Isao
authors.initials: I
authors.lastname: Tanaka
authors.affiliation: Faculty of Advanced Life Science andGraduate School of Life Sciences, Hokkaido University, Sapporo 060-0810, Japan dieter.soll@yale.edu yao@castor.sci.hokudai.ac.jp.
authors.forename: Min
authors.initials: M
authors.lastname: Yao
authors.affiliation: Departments of Molecular Biophysics and Biochemistry andChemistry, Yale University, New Haven, CT 06520; and dieter.soll@yale.edu yao@castor.sci.hokudai.ac.jp.
authors.forename: Dieter
authors.initials: D
authors.lastname: Söll
mesh_terms: D000107:Acetylation; D001105:Archaea / Q000378:metabolism*; D019843:Archaeal Proteins / Q000737:chemistry / Q000378:metabolism*; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000096:biosynthesis*; D007700:Kinetics; D017017:Methanococcus / Q000378:metabolism*; D008958:Models, Molecular; D010448:Peptide Initiation Factors / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012350:RNA, Transfer, Cys / Q000737:chemistry / Q000378:metabolism*
chemical_list: D019843:Archaeal Proteins; D010448:Peptide Initiation Factors; D012350:RNA, Transfer, Cys; D003545:Cysteine
keywords: aminoacyl-tRNA; methanogen; protein complex