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Structure of selenocysteine synthase from Escherichia coli and location of tRNA in the seryl‐tRNA sec –enzyme complex
Author(s) -
Engelhardt Harald,
Forchhammer Karl,
Müller Shirley,
Goldie Kenneth N.,
Böck August
Publication year - 1992
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1992.tb01781.x
Subject(s) - selenocysteine , transfer rna , biology , enzyme , biochemistry , escherichia coli , dimer , stereochemistry , chemistry , rna , gene , organic chemistry , cysteine
Summary Selenocysteine synthase of Escherichia coli catalyses the biosynthesis of selenocysteine in the form of the aminoacyl‐RNA complex, the reaction intermediate being aminoacrylyl‐tRNA sec covalently bound to the prosthetic group of the enzyme. Selenocysteine synthase and the specific aminoacrylyl‐tRNA sec ‐enzyme complex as well as the isolated seryl‐tRNA sec were investigated in the electron microscope and analysed by means of image processing to a resolution of 2 nm in projection. The stoichiometric composition of the selenocysteine synthase molecule was elucidated by scanning transmission electron microscopic mass determination. The enzyme has a fivefold symmetric structure and consists of 10 monomers arranged in two rings. The tRNA is bound near the margin of the dimeric subunits. Principal component analysis of the tRNA‐enzyme complexes revealed that the selenocysteine synthase appears to bind only one seryl‐tRNA sec per dimer, which is consistent with the result of biochemical binding studies.