Structural basis for dynamic interdomain movement and RNA recognition of the selenocysteine-specific elongation factor SelB.
Selenocysteine (Sec) is the "21st" amino acid and is genetically encoded by an unusual incorporation system. The stop codon UGA becomes a Sec codon when the selenocysteine insertion sequence (SECIS) exists downstream of UGA. Sec incorporation requires a specific elongation factor, SelB, which recognizes tRNA(Sec) via use of an EF-Tu-like domain and the SECIS mRNA hairpin via use of a C-terminal domain (SelB-C). SelB functions in multiple translational steps: binding to SECIS mRNA and tRNA(Sec), delivery of tRNA(Sec) onto an A site, GTP hydrolysis, and release from tRNA and mRNA. However, this dynamic mechanism remains to be revealed. Here, we report a large domain rearrangement in the structure of SelB-C complexed with RNA. Surprisingly, the interdomain region forms new interactions with the phosphate backbone of a neighboring RNA, distinct from SECIS RNA binding. This SelB-RNA interaction is sequence independent, possibly reflecting SelB-tRNA/-rRNA recognitions. Based on these data, the dynamic SelB-ribosome-mRNA-tRNA interactions will be discussed.
Ose
Toyoyuki
T
Division of Structural Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan.
Soler
Nicolas
N
Rasubala
Linda
L
Kuroki
Kimiko
K
Kohda
Daisuke
D
Fourmy
Dominique
D
Yoshizawa
Satoko
S
Maenaka
Katsumi
K
D001419:Bacteria / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D011485:Protein Binding / Q000502:physiology; D012313:RNA / Q000378:metabolism*; D017279:Selenocysteine / Q000378:metabolism*
D001426:Bacterial Proteins; C061878:SelB protein, Bacteria; D017279:Selenocysteine; D012313:RNA