title: The selenocysteine-specific elongation factor contains a novel and multi-functional domain.
abstract: The selenocysteine (Sec)-specific eukaryotic elongation factor (eEFSec) delivers the aminoacylated selenocysteine-tRNA (Sec-tRNA(Sec)) to the ribosome and suppresses UGA codons that are upstream of Sec insertion sequence (SECIS) elements bound by SECIS-binding protein 2 (SBP2). Multiple studies have highlighted the importance of SBP2 forming a complex with the SECIS element, but it is not clear how this regulates eEFSec during Sec incorporation. Compared with the canonical elongation factor eEF1A, eEFSec has a unique C-terminal extension called Domain IV. To understand the role of Domain IV in Sec incorporation, we examined a series of mutant proteins for all of the known molecular functions for eEFSec: GTP hydrolysis, Sec-tRNA(Sec) binding, and SBP2/SECIS binding. In addition, wild-type and mutant versions of eEFSec were analyzed for Sec incorporation activity in a novel eEFSec-dependent translation extract. We have found that Domain IV is essential for both tRNA and SBP2 binding as well as regulating GTPase activity. We propose a model where the SBP2/SECIS complex activates eEFSec by directing functional interactions between Domain IV and the ribosome to promote Sec-tRNA(Sec) binding and accommodation into the ribosomal A-site.
authors.affiliation: Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA.
authors.forename: Jonathan N
authors.initials: JN
authors.lastname: Gonzalez-Flores
authors.forename: Nirupama
authors.initials: N
authors.lastname: Gupta
authors.forename: Louise W
authors.initials: LW
authors.lastname: DeMong
authors.forename: Paul R
authors.initials: PR
authors.lastname: Copeland
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003062:Codon; D018388:Codon, Terminator; D003432:Cross-Linking Reagents / Q000737:chemistry; D006160:Guanosine Triphosphate / Q000737:chemistry; D006868:Hydrolysis; D051379:Mice; D008969:Molecular Sequence Data; D010445:Peptide Elongation Factors / Q000737:chemistry* / Q000378:metabolism; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry; D016601:RNA-Binding Proteins / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry; D012270:Ribosomes / Q000737:chemistry; D017279:Selenocysteine / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid
chemical_list: D003062:Codon; D018388:Codon, Terminator; D003432:Cross-Linking Reagents; C509159:EFsec protein, mouse; D010445:Peptide Elongation Factors; D012346:RNA, Transfer, Amino Acyl; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; C577859:SECIS-binding protein 2, mouse; C498488:Secisbp2 protein, rat; C112705:selenocysteinyl-tRNA; D017279:Selenocysteine; D006160:Guanosine Triphosphate