Anupama K Puppala, Dylan Sosa, Jennifer Castillo Suchkou, Rachel L French, Malgorzata Dobosz-Bartoszek, Kaitlyn A Kiernan, Miljan Simonović
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引用次数: 0
Abstract
The evolution of the genetic code to incorporate selenocysteine (Sec) enabled the development of a selenoproteome in all domains of life. O-phosphoseryl-tRNASec selenium transferase (SepSecS) catalyzes the terminal reaction of Sec synthesis on tRNASec in archaea and eukaryotes. Despite harboring four equivalent active sites, human SEPSECS binds no more than two tRNASec molecules. Though, the basis for this asymmetry remains poorly understood. In humans, an acidic, C-terminal, α-helical extension precludes additional tRNA-binding events in two of the enzyme monomers, stabilizing the SEPSECS•tRNASec complex. However, the existence of a helix exclusively in vertebrates raised questions about the evolution of the tRNA-binding mechanism in SEPSECS and the origin of its C-terminal extension. Herein, using a comparative structural and phylogenetic analysis, we show that the tRNA-binding motifs in SEPSECS are poorly conserved across species. Consequently, in contrast to mammalian SEPSECS, the archaeal ortholog cannot bind unacylated tRNASec and requires an aminoacyl group. Moreover, the C-terminal α-helix 16 is a mammalian innovation, and its absence causes aggregation of the SEPSECS•tRNASec complex at low tRNA concentrations. Altogether, we propose SEPSECS evolved a tRNASec binding mechanism as a crucial functional and structural feature, allowing for additional levels of regulation of Sec and selenoprotein synthesis.
期刊介绍:
Nucleic Acids Research (NAR) is a scientific journal that publishes research on various aspects of nucleic acids and proteins involved in nucleic acid metabolism and interactions. It covers areas such as chemistry and synthetic biology, computational biology, gene regulation, chromatin and epigenetics, genome integrity, repair and replication, genomics, molecular biology, nucleic acid enzymes, RNA, and structural biology. The journal also includes a Survey and Summary section for brief reviews. Additionally, each year, the first issue is dedicated to biological databases, and an issue in July focuses on web-based software resources for the biological community. Nucleic Acids Research is indexed by several services including Abstracts on Hygiene and Communicable Diseases, Animal Breeding Abstracts, Agricultural Engineering Abstracts, Agbiotech News and Information, BIOSIS Previews, CAB Abstracts, and EMBASE.