Recognition of the mRNA selenocysteine insertion sequence by the specialized translational elongation factor SELB.
In Escherichia coli the unusual amino acid selenocysteine is incorporated cotranslationally at an in-frame UGA codon. Incorporation of selenocysteine relies, in part, on the interaction between a specialized elongation factor, the SELB protein, and a cis-acting element within the mRNA. Boundary and toeprint experiments illustrate that the SELB-GTP-Sec-tRNA(Sec) ternary complex binds to the selenoprotein encoding mRNAs fdhF and fdnG, serving to increase the concentration of SELB and Sec-tRNA(Sec) on these mRNAs in vivo. Moreover, toeprint experiments indicate that SELB recognizes the ribosome-bound message and that, upon binding, SELB may protrude out of the ribosomal-mRNA track so as to approach the large ribosomal subunit. The results place the mRNA-bound SELB-GTP-Sec-tRNA(Sec) ternary complex at the selenocysteine codon (as expected) and suggest a mechanism to explain the specificity of selenocysteine insertion. Cis-acting mRNA regulatory elements can tether protein factors to the translation complex during protein synthesis.
Ringquist
S
S
Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder 80309.
Schneider
D
D
Gibson
T
T
Baron
C
C
Böck
A
A
Gold
L
L
D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D003062:Codon; D004926:Escherichia coli / Q000235:genetics; D008969:Molecular Sequence Data; D010441:Peptide Chain Elongation, Translational / Q000502:physiology; D010442:Peptide Chain Initiation, Translational / Q000502:physiology*; D010445:Peptide Elongation Factors / Q000378:metabolism*; D011485:Protein Binding; D014176:Protein Biosynthesis; D011506:Proteins; D012333:RNA, Messenger / Q000378:metabolism*; D012345:RNA, Transfer, Amino Acid-Specific; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D012358:RNA, Transfer, Met / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D017279:Selenocysteine / Q000235:genetics / Q000378:metabolism*; D051140:Selenoproteins; D017423:Sequence Analysis, RNA
D001426:Bacterial Proteins; D003062:Codon; D010445:Peptide Elongation Factors; D011506:Proteins; D012333:RNA, Messenger; D012345:RNA, Transfer, Amino Acid-Specific; D012346:RNA, Transfer, Amino Acyl; D012358:RNA, Transfer, Met; D012269:Ribosomal Proteins; C061878:SelB protein, Bacteria; D051140:Selenoproteins; C040469:ribosomal protein S30; C112705:selenocysteinyl-tRNA; C036928:tRNA, selenocysteine-; D017279:Selenocysteine