Structural highlights
Publication Abstract from PubMedEukaryal translation initiation factor 2B (eIF2B) acts as guanine nucleotide exchange factor (GEF) for eIF2 and forms a central target for pathways regulating global protein synthesis. eIF2B consists of five non-identical subunits (alpha-), which assemble into a catalytic subcomplex (gamma, ) responsible for the GEF activity, and a regulatory subcomplex (alpha, beta, delta) which regulates the GEF activity under stress conditions. Here, we provide new structural and functional insight into the regulatory subcomplex of eIF2B (eIF2BRSC). We report the crystal structures of eIF2Bbeta and eIF2Bdelta from Chaetomium thermophilum as well as the crystal structure of their tetrameric eIF2B(betadelta)2 complex. Combined with mutational and biochemical data, we show that eIF2BRSC exists as a hexamer in solution, consisting of two eIF2Bbetadelta heterodimers and one eIF2Balpha2 homodimer, which is homologous to homohexameric ribose 1,5-bisphosphate isomerases. This homology is further substantiated by the finding that eIF2Balpha specifically binds AMP and GMP as ligands. Based on our data, we propose a model for eIF2BRSC and its interactions with eIF2 that is consistent with previous biochemical and genetic data and provides a framework to better understand eIF2B function, the molecular basis for Gcn-, Gcd- and VWM/CACH mutations and the evolutionary history of the eIF2B complex. Architecture of the eIF2B regulatory subcomplex and its implications for the regulation of guanine nucleotide exchange on eIF2.,Kuhle B, Eulig NK, Ficner R Nucleic Acids Res. 2015 Sep 17. pii: gkv930. PMID:26384431[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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