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EF-G

ef-g protein, ef-gradiva
EF-G elongation factor G, historically known as translocase is a prokaryotic elongation factor and a GTPase responsible for catalyzing the coordinated movement of transfer RNA tRNA and messenger RNA mRNA through the ribosome during the elongation step of protein translation

Contents

  • 1 Structure
    • 11 EF-G on the ribosome
      • 111 Binding to L7/L12
      • 112 Interaction with the GTPase Associated Center
  • 2 Function in protein elongation
  • 3 Function in protein termination
  • 4 Clinical significance
  • 5 Evolution
  • 6 See also
  • 7 References
  • 8 External links

Structure

Encoded by the fusA gene, EF-G is made up of 704 amino acids that form 5 domains, labeled Domain I through Domain V Domain I may be referred to as the G-domain or as Domain IG, since it binds to and hydrolyzes guanosine triphosphate GTP Domain I also helps EF-G bind to the ribosome, and contains the N-terminal of the polypeptide chain Domain IV is important for translocation, as it undergoes a significant conformational change and enters the A site on the 30S ribosomal subunit, pushing the mRNA and tRNA molecules from the A site to the P site

The five domains may be also separated into two super-domains Super-domain I consists of Domains I and II, and super-domain II consists of Domains III - IV Throughout translocation, super-domain I will remain relatively unchanged, as it is responsible for binding tightly to the ribosome However, super-domain II will undergo a large rotational motion from the pre-translocational PRE state to the post-translocational POST state

Crystal structure of EF-G in the POST state with Domains I -V labeled PDB ID: 4V5F

EF-G on the ribosome

Binding to L7/L12

L7/L12 is a protein on the large ribosomal subunit that binds to certain GTPases, like Initiation Factor 2, Release Factor 3, and Domain I of EF-G Specifically, the C-terminal of L7/L12 will bind to EF-G and is necessary for GTP hydrolysis

Interaction with the GTPase Associated Center

The GTPase Associated Center GAC is a region on the large ribosomal subunit that consists of two smaller regions of 23S ribosomal RNA called the L11 stalk and the sarcin-ricin loop SRL As a highly conserved rRNA loop in evolution, the SRL is critical in helping GTPases bind to the ribosome, but is not essential for GTP hydrolysis There is some evidence to support that a phosphate oxygen in the A2662 residue of the SRL may help hydrolyze GTP

Function in protein elongation

EF-G catalyzes the translocation of the tRNA and mRNA down the ribosome at the end of each round of polypeptide elongation In this process, the peptidyl transferase center PTC has catalyzed the formation of a peptide bond between amino acids, moving the polypeptide chain from the P site tRNA to the A site tRNA The 50S and 30S ribosomal subunits are now allowed to rotate relative to each other by approximately 7° The subunit rotation is coupled with the movement of the 3' ends of both tRNA molecules on the large subunit from the A and P sites to the P and E sites, respectively, while the anticodon loops remain unshifted This rotated ribosomal intermediate, in which the first tRNA occupies a hybrid A/P position and the second tRNA occupies a hybrid P/E position is a substrate for EF-G-GTP

As a GTPase, EF-G binds to the rotated ribosome near the A site in its GTP-bound state, and hydrolyzes GTP, releasing GDP and inorganic phosphate:

GTP + H2O ↔ GDP + Pi

The hydrolysis of GTP allows for a large conformational change within EF-G, forcing the A/P tRNA to fully occupy the P site, the P/E tRNA to fully occupy the E site and exit the ribosome complex, and the mRNA to shift three nucleotides down relative to the ribosome The GDP-bound EF-G molecule then dissociates from the complex, leaving another free A-site where the elongation cycle can start again

Crystal structure of the ribosome with two tRNAs orange and green and EF-G in cyan after translocation PDB ID: 4W29

Function in protein termination

Protein elongation continues until a stop codon appears on the mRNA A Class I release factor RF1 or RF2 binds to the stop codon, which induces hydrolysis of the tRNA-peptide bond in the P site, allowing the newly-formed protein to exit the ribosome The nascent peptide continues to fold and leaves the 70S ribosome, the mRNA, the deacylated tRNA P site, and the Class I release factor A site

In a GTP-dependent manner, the subsequent recycling is catalyzed by a Class II release factor named Ribosome Recycling Factor RRF, also called RF3, Initiation Factor 3 IF3 and EF-G The protein RF3 releases the Class I release factor so that it may occupy the ribosomal A site EF-G hydrolyzes GTP and undergoes a large conformational change to push RF3 down the ribosome, which occurs alongside tRNA dissociation and promotes the ribosomal subunit rotation This motion actively splits the B2a/B2b bridge, which connects the 30S and the 50S subunits, so that the ribosome can split IF3 then isolates the 30S subunit to prevent re-association of the large and small subunits

Clinical significance

It is normally inhibited by fusidic acid, but resistance has emerged

Evolution

EF-G has a complex evolutionary history, with numerous paralogous versions of the factor present in bacteria, suggesting subfunctionalization of different EF-G variants

See also

  • Prokaryotic elongation factors
  • EF-Ts elongation factor thermo stable
  • EF-Tu elongation factor thermo unstable
  • EF-P elongation factor P
  • eEF2 eukaryotic elongation factor 2
  • Protein translation
  • GTPase

References

  1. ^ a b c d Shoji, S; Walker, SE; Fredrick, K 2009 "Ribosomal translocation: one step closer to the molecular mechanism" ACS Chem Biol 4: 93–107 doi:101021/cb8002946 PMC 3010847  PMID 19173642 
  2. ^ "fusA - Elongation factor G - Escherichia coli strain K12 - fusA gene & protein" wwwuniprotorg Retrieved 2018-04-07 
  3. ^ Liu, Kaixian; Rehfus, Joseph E; Mattson, Elliot; Kaiser, Christian M 2017-07-01 "The ribosome destabilizes native and non-native structures in a nascent multidomain protein" Protein Science 26 7: 1439–1451 doi:101002/pro3189 ISSN 1469-896X 
  4. ^ a b Carlson, Markus A; Haddad, Bassam G; Weis, Amanda J; Blackwood, Colby S; Shelton, Catherine D; Wuerth, Michelle E; Walter, Justin D; Spiegel, Paul Clint 2017-06-01 "Ribosomal protein L7/L12 is required for GTPase translation factors EF-G, RF3, and IF2 to bind in their GTP state to 70S ribosomes" The FEBS Journal 284 11: 1631–1643 doi:101111/febs14067 ISSN 1742-4658 
  5. ^ Salsi, Enea; Farah, Elie; Dann, Jillian; Ermolenko, Dmitri N "Following movement of domain IV of elongation factor G during ribosomal translocation" Proceedings of the National Academy of Sciences 111 42: 15060–15065 doi:101073/pnas1410873111 
  6. ^ Lin, Jinzhong; Gagnon, Matthieu G; Bulkley, David; Steitz, Thomas A "Conformational Changes of Elongation Factor G on the Ribosome during tRNA Translocation" Cell 160 1-2: 219–227 doi:101016/jcell201411049 
  7. ^ Li, Wen; Trabuco, Leonardo G; Schulten, Klaus; Frank, Joachim 2011-05-01 "Molecular dynamics of EF-G during translocation" Proteins: Structure, Function, and Bioinformatics 79 5: 1478–1486 doi:101002/prot22976 ISSN 1097-0134 
  8. ^ Zhang, Dejiu; Yan, Kaige; Zhang, Yiwei; Liu, Guangqiao; Cao, Xintao; Song, Guangtao; Xie, Qiang; Gao, Ning; Qin, Yan "New insights into the enzymatic role of EF-G in ribosome recycling" Nucleic Acids Research doi:101093/nar/gkv995 
  9. ^ Maklan, E J 2012 Genetic and Biochemical Analysis of the GTPase Associated Center of the Ribosome UC Santa Cruz ProQuest ID: Maklan_ucsc_0036E_10006 Merritt ID: ark:/13030/m5js9t4d Retrieved from https://escholarshiporg/uc/item/7gh9v43h
  10. ^ Shi, Xinying; Khade, Prashant K; Sanbonmatsu, Karissa Y; Joseph, Simpson "Functional Role of the Sarcin–Ricin Loop of the 23S rRNA in the Elongation Cycle of Protein Synthesis" Journal of Molecular Biology 419 3-4: 125–138 doi:101016/jjmb201203016 
  11. ^ a b Choi, Junhong; Puglisi, Joseph D "Three tRNAs on the ribosome slow translation elongation" Proceedings of the National Academy of Sciences 114 52: 13691–13696 doi:101073/pnas1719592115 
  12. ^ Guo, Z; Noller, H F "Rotation of the head of the 30S ribosomal subunit during mRNA translocation" Proceedings of the National Academy of Sciences 109 50: 20391–20394 doi:101073/pnas1218999109 
  13. ^ da Cunha, CE; Belardinelli, R; Peske, F; Holtkamp, W; Wintermeyer, W; Rodnina, MV 2013 "Dual use of GTP hydrolysis by elongation factor G on the ribosome" Translation 1: e24315 doi:104161/trla24315 
  14. ^ a b Das, Debasis; Samanta, Dibyendu; Bhattacharya, Arpita; Basu, Arunima; Das, Anindita; Ghosh, Jaydip; Chakrabarti, Abhijit; Gupta, Chanchal Das 2017-01-18 "A Possible Role of the Full-Length Nascent Protein in Post-Translational Ribosome Recycling" PLOS ONE 12 1: e0170333 doi:101371/journalpone0170333 ISSN 1932-6203 
  15. ^ Zavialov AV, Hauryliuk VV, Ehrenberg M 2005 "Splitting of the posttermination ribosome into subunits by the concerted action of RRF and EF-G" Molecular Cell 18 6: 675–686 doi:101016/jmolcel200505016 PMID 15949442 
  16. ^ Hirokawa, Go; Nijman, Romana M; Raj, V Samuel; Kaji, Hideko; Igarashi, Kazuei; Kaji, Akira 2005-08-01 "The role of ribosome recycling factor in dissociation of 70S ribosomes into subunits" RNA 11 8: 1317–1328 doi:101261/rna2520405 ISSN 1355-8382 PMID 16043510 
  17. ^ Macvanin M, Hughes D June 2005 "Hyper-susceptibility of a fusidic acid-resistant mutant of Salmonella to different classes of antibiotics" FEMS Microbiology Letters 247 2: 215–20 doi:101016/jfemsle200505007 PMID 15935566 
  18. ^ Macvanin M, Johanson U, Ehrenberg M, Hughes D July 2000 "Fusidic acid-resistant EF-G perturbs the accumulation of ppGpp" Molecular Microbiology 37 1: 98–107 doi:101046/j1365-2958200001967x PMID 10931308 
  19. ^ G C Atkinson; S L Baldauf 2011 "Evolution of elongation factor G and the origins of mitochondrial and chloroplast forms" Molecular Biology and Evolution 28 3: 1281–92 doi:101093/molbev/msq316 PMID 21097998 

External links

  • Peptide Elongation Factor G at the US National Library of Medicine Medical Subject Headings MeSH

ef-g binding to ribosome, ef-g ef-tu, ef-g elongation factor, ef-g protein, ef-g structure, ef-g-gtp, ef-g5, ef-gaez ecosystem, ef-gradiva, ef-gsm ltd


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EF-G


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    EF-G beatiful post thanks!

    29.10.2014


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