Structure of selenocysteine synthase from Escherichia coli and location of tRNA in the seryl-tRNA(sec)-enzyme complex.
Selenocysteine synthase of Escherichia coli catalyses the biosynthesis of selenocysteine in the form of the aminoacyl-tRNA 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.
Engelhardt
H
H
Max-Planck-Institut für Biochemie, Martinsried, Germany.
Forchhammer
K
K
Müller
S
S
Goldie
K N
KN
Böck
A
A
D001426:Bacterial Proteins / Q000648:ultrastructure; D004926:Escherichia coli / Q000201:enzymology*; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D008970:Molecular Weight; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D014166:Transferases / Q000378:metabolism / Q000648:ultrastructure*
D001426:Bacterial Proteins; D012346:RNA, Transfer, Amino Acyl; D014166:Transferases; C060600:selenium transferase