Bacterial initiation factor

A bacterial initiation factor (IF) is a protein that stabilizes the initiation complex for polypeptide translation.

Translation initiation is essential to protein synthesis and regulates mRNA translation fidelity and efficiency in bacteria.[1] The 30S ribosomal subunit, initiator tRNA, and mRNA form an initiation complex for elongation.[2] This complex process requires three essential protein factors in bacteria – IF1, IF2, and IF3.[3] These factors bind to the 30S subunit and promote correct initiation codon selection on the mRNA.[4] IF1, the smallest factor at 8.2 kDa, blocks elongator tRNA binding at the A-site.[5] IF2 is the major component that transports initiator tRNA to the P-site.[6] IF3 checks P-site codon-anticodon pairing and rejects incorrect initiation complexes.[7]

The orderly mechanism of initiation starts with IF3 attaching to the 30S subunit and changing its shape.[8] IF1 joins next, followed by mRNA binding, and starts codon-P-site interaction.[9] IF2 enters with the initiator tRNA and places it on the start codon.[6] GTP hydrolysis by IF2 releases it and IF3, enabling 50S subunit joining.[10] The coordinated binding and activities of IF1, IF2, and IF3 are essential for the rapid and precise translation initiation in bacteria. They facilitate start codon selection and assemble an active, protein-synthesis-ready 70S ribosome.

  1. ^ Laursen BS, Sørensen HP, Mortensen KK, Sperling-Petersen HU (March 2005). "Initiation of protein synthesis in bacteria". Microbiology and Molecular Biology Reviews. 69 (1): 101–123. doi:10.1128/mmbr.69.1.101-123.2005. PMC 1082788. PMID 15755955.
  2. ^ Steitz JA, Jakes K (December 1975). "How ribosomes select initiator regions in mRNA: base pair formation between the 3' terminus of 16S rRNA and the mRNA during initiation of protein synthesis in Escherichia coli". Proceedings of the National Academy of Sciences of the United States of America. 72 (12): 4734–4738. Bibcode:1975PNAS...72.4734S. doi:10.1073/pnas.72.12.4734. PMC 388805. PMID 1107998.
  3. ^ Gualerzi CO, Pon CL (June 1990). "Initiation of mRNA translation in prokaryotes". Biochemistry. 29 (25): 5881–5889. doi:10.1021/bi00477a001. PMID 2200518.
  4. ^ McCarthy JE, Brimacombe R (November 1994). "Prokaryotic translation: the interactive pathway leading to initiation". Trends in Genetics. 10 (11): 402–407. doi:10.1016/0168-9525(94)90057-4. PMID 7809946.
  5. ^ Celano B, Pawlik RT, Gualerzi CO (December 1988). "Interaction of Escherichia coli translation-initiation factor IF-1 with ribosomes". European Journal of Biochemistry. 178 (2): 351–355. doi:10.1111/j.1432-1033.1988.tb14457.x. PMID 3061814.
  6. ^ a b La Teana A, Pon CL, Gualerzi CO (March 1996). "Late events in translation initiation. Adjustment of fMet-tRNA in the ribosomal P-site". Journal of Molecular Biology. 256 (4): 667–675. doi:10.1006/jmbi.1996.0116. PMID 8642589.
  7. ^ Sussman JK, Simons EL, Simons RW (July 1996). "Escherichia coli translation initiation factor 3 discriminates the initiation codon in vivo". Molecular Microbiology. 21 (2): 347–360. doi:10.1046/j.1365-2958.1996.6371354.x. PMID 8858589. S2CID 31289254.
  8. ^ Fabbretti A, Pon CL, Hennelly SP, Hill WE, Lodmell JS, Gualerzi CO (January 2007). "The real-time path of translation factor IF3 onto and off the ribosome". Molecular Cell. 25 (2): 285–296. doi:10.1016/j.molcel.2006.12.011. PMID 17244535.
  9. ^ La Teana A, Gualerzi CO, Brimacombe R (October 1995). "From stand-by to decoding site. Adjustment of the mRNA on the 30S ribosomal subunit under the influence of the initiation factors". RNA. 1 (8): 772–782. PMC 1369318. PMID 7493323.
  10. ^ Antoun A, Pavlov MY, Andersson K, Tenson T, Ehrenberg M (October 2003). "The roles of initiation factor 2 and guanosine triphosphate in initiation of protein synthesis". The EMBO Journal. 22 (20): 5593–5601. doi:10.1093/emboj/cdg525. PMC 213779. PMID 14532131.