Aminoacylation of tRNA with phosphoserine for synthesis of cysteinyl-tRNA(Cys).
Cysteinyl-tRNA(Cys) (Cys-tRNA(Cys)) is required for translation and is typically synthesized by cysteinyl-tRNA synthetase (CysRS). However, Methanocaldococcus jannaschii synthesizes Cys-tRNA(Cys) by an indirect pathway, whereby O-phosphoseryl-tRNA synthetase (SepRS) acylates tRNA(Cys) with phosphoserine (Sep), and Sep-tRNA-Cys-tRNA synthase (SepCysS) converts the tRNA-bound phosphoserine to cysteine. We show here that M. jannaschii SepRS differs from CysRS by recruiting the m1G37 modification as a determinant for aminoacylation, and in showing limited discrimination against mutations of conserved nucleotides. Kinetic and binding measurements show that both SepRS and SepCysS bind the reaction intermediate Sep-tRNA(Cys) tightly, and these two enzymes form a stable binary complex that promotes conversion of the intermediate to the product and sequesters the intermediate from binding to elongation factor EF-1alpha or infiltrating into the ribosome. These results highlight the importance of the protein binary complex for efficient synthesis of Cys-tRNA(Cys).
Zhang
Chun-Mei
CM
Department of Biochemistry and Molecular Biology, 233 South 10th Street, Philadelphia, Pennsylvania 19107, USA.
Liu
Cuiping
C
Slater
Simon
S
Hou
Ya-Ming
YM
D049148:Aminoacylation; D001483:Base Sequence; D004252:DNA Mutational Analysis; D007700:Kinetics; D017016:Methanococcaceae / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes; D009690:Nucleic Acid Conformation; D010768:Phosphoserine / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry / Q000378:metabolism*
D046912:Multiprotein Complexes; D012346:RNA, Transfer, Amino Acyl; D010768:Phosphoserine