Publication Date:
2013-04-06
Description:
The 21st amino acid, selenocysteine (Sec), is synthesized on its cognate transfer RNA (tRNA(Sec)). In bacteria, SelA synthesizes Sec from Ser-tRNA(Sec), whereas in archaea and eukaryotes SepSecS forms Sec from phosphoserine (Sep) acylated to tRNA(Sec). We determined the crystal structures of Aquifex aeolicus SelA complexes, which revealed a ring-shaped homodecamer that binds 10 tRNA(Sec) molecules, each interacting with four SelA subunits. The SelA N-terminal domain binds the tRNA(Sec)-specific D-arm structure, thereby discriminating Ser-tRNA(Sec) from Ser-tRNA(Ser). A large cleft is created between two subunits and accommodates the 3'-terminal region of Ser-tRNA(Sec). The SelA structures together with in vivo and in vitro enzyme assays show decamerization to be essential for SelA function. SelA catalyzes pyridoxal 5'-phosphate-dependent Sec formation involving Arg residues nonhomologous to those in SepSecS. Different protein architecture and substrate coordination of the bacterial enzyme provide structural evidence for independent evolution of the two Sec synthesis systems present in nature.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3976565/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉 〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3976565/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Itoh, Yuzuru -- Brocker, Markus J -- Sekine, Shun-ichi -- Hammond, Gifty -- Suetsugu, Shiro -- Soll, Dieter -- Yokoyama, Shigeyuki -- GM22854/GM/NIGMS NIH HHS/ -- R01 GM022854/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2013 Apr 5;340(6128):75-8. doi: 10.1126/science.1229521.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉RIKEN Systems and Structural Biology Center, Tsurumi, Yokohama 230-0045, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23559248" target="_blank"〉PubMed〈/a〉
Keywords:
Arginine/chemistry
;
Bacteria/*enzymology
;
Bacterial Proteins/*chemistry
;
Catalysis
;
Catalytic Domain
;
Crystallography, X-Ray
;
Protein Multimerization
;
Protein Structure, Secondary
;
Protein Structure, Tertiary
;
Pyridoxal Phosphate/chemistry
;
RNA, Transfer, Amino Acyl/*chemistry
;
Selenocysteine/*biosynthesis
;
Transferases/*chemistry
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
Permalink