Function of initiation factor 1 in the binding and release of initiation factor 2 from ribosomal initiation complexes in Escherichia coli

E. A. Stringer, P. Sarkar, U. Maitra

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Studies on the function of initiation factor 1 (IF 1) in the formation of 30 S initiation complexes have been carried out. IF 1 appears to prevent the dissociation of initiation factor 2 (IF 2) from the 30 S initiation complex. The factor has no effect on either the initial binding of IF 2 nor does it increase the amount of IF 2 dependent fMet tRNA and GTP bound to the 30 S subunit. Bound fMet tRNA remains stable to sucrose gradient centrifugation even in the absence of IF 1. It is postulated that the presence of IF 2 on the 30 S complex is necessary so that at the time of junction with the 50 S subunit to form a 70 S complex, the 70 S dependent GTPase activity of IF 2 can hydrolyze GTP. This hydrolysis provides a means by which GTP can be removed to facilitate formation of a 70 S initiation complex active in peptidyl transfer. In support of this postulate, it was observed that 30 S initiation complexes formed in the absence of IF 1 could be depleted of their complement of GTP and IF 2. Such depleted initiation complexes were still able to accept 50 S subunits to form 70 S complexes which could still donate fMet tRNA into peptide linkages. These results indicate that 30 S complexes lacking GTP do not require IF 2 for formation of active 70 S complexes. IF 1, which is required to prevent dissociation of IF 2 from the 30 S initiation complex, is also required for release of IF 2 from ribosomes following 70 S initiation complex formation. The mechanism of the release of IF 2 has been studied in greater detail. Evidence is presented which rules out the presence of a stable IF 2 GDP complex on the surface of the 70 S ribosome following GTP hydrolysis and of any exchange reactions between IF 1 and guanine nucleotides necessary for effecting the release of IF 2. IF 2 remains on the 70 S initiation complexes after release of guanine nucleotides and can be liberated solely by addition of IF 1.

Original languageEnglish (US)
Pages (from-to)1739-1744
Number of pages6
JournalJournal of Biological Chemistry
Volume252
Issue number5
StatePublished - 1977

Fingerprint

Prokaryotic Initiation Factor-2
Peptide Initiation Factors
Escherichia coli
Guanosine Triphosphate
Guanine Nucleotides
Ribosomes
peptide chain termination release factor 2
Hydrolysis
Centrifugation
GTP Phosphohydrolases

ASJC Scopus subject areas

  • Biochemistry

Cite this

Function of initiation factor 1 in the binding and release of initiation factor 2 from ribosomal initiation complexes in Escherichia coli. / Stringer, E. A.; Sarkar, P.; Maitra, U.

In: Journal of Biological Chemistry, Vol. 252, No. 5, 1977, p. 1739-1744.

Research output: Contribution to journalArticle

@article{490edcc01b814f2f8286faeb4256bd6b,
title = "Function of initiation factor 1 in the binding and release of initiation factor 2 from ribosomal initiation complexes in Escherichia coli",
abstract = "Studies on the function of initiation factor 1 (IF 1) in the formation of 30 S initiation complexes have been carried out. IF 1 appears to prevent the dissociation of initiation factor 2 (IF 2) from the 30 S initiation complex. The factor has no effect on either the initial binding of IF 2 nor does it increase the amount of IF 2 dependent fMet tRNA and GTP bound to the 30 S subunit. Bound fMet tRNA remains stable to sucrose gradient centrifugation even in the absence of IF 1. It is postulated that the presence of IF 2 on the 30 S complex is necessary so that at the time of junction with the 50 S subunit to form a 70 S complex, the 70 S dependent GTPase activity of IF 2 can hydrolyze GTP. This hydrolysis provides a means by which GTP can be removed to facilitate formation of a 70 S initiation complex active in peptidyl transfer. In support of this postulate, it was observed that 30 S initiation complexes formed in the absence of IF 1 could be depleted of their complement of GTP and IF 2. Such depleted initiation complexes were still able to accept 50 S subunits to form 70 S complexes which could still donate fMet tRNA into peptide linkages. These results indicate that 30 S complexes lacking GTP do not require IF 2 for formation of active 70 S complexes. IF 1, which is required to prevent dissociation of IF 2 from the 30 S initiation complex, is also required for release of IF 2 from ribosomes following 70 S initiation complex formation. The mechanism of the release of IF 2 has been studied in greater detail. Evidence is presented which rules out the presence of a stable IF 2 GDP complex on the surface of the 70 S ribosome following GTP hydrolysis and of any exchange reactions between IF 1 and guanine nucleotides necessary for effecting the release of IF 2. IF 2 remains on the 70 S initiation complexes after release of guanine nucleotides and can be liberated solely by addition of IF 1.",
author = "Stringer, {E. A.} and P. Sarkar and U. Maitra",
year = "1977",
language = "English (US)",
volume = "252",
pages = "1739--1744",
journal = "Journal of Biological Chemistry",
issn = "0021-9258",
publisher = "American Society for Biochemistry and Molecular Biology Inc.",
number = "5",

}

TY - JOUR

T1 - Function of initiation factor 1 in the binding and release of initiation factor 2 from ribosomal initiation complexes in Escherichia coli

AU - Stringer, E. A.

AU - Sarkar, P.

AU - Maitra, U.

PY - 1977

Y1 - 1977

N2 - Studies on the function of initiation factor 1 (IF 1) in the formation of 30 S initiation complexes have been carried out. IF 1 appears to prevent the dissociation of initiation factor 2 (IF 2) from the 30 S initiation complex. The factor has no effect on either the initial binding of IF 2 nor does it increase the amount of IF 2 dependent fMet tRNA and GTP bound to the 30 S subunit. Bound fMet tRNA remains stable to sucrose gradient centrifugation even in the absence of IF 1. It is postulated that the presence of IF 2 on the 30 S complex is necessary so that at the time of junction with the 50 S subunit to form a 70 S complex, the 70 S dependent GTPase activity of IF 2 can hydrolyze GTP. This hydrolysis provides a means by which GTP can be removed to facilitate formation of a 70 S initiation complex active in peptidyl transfer. In support of this postulate, it was observed that 30 S initiation complexes formed in the absence of IF 1 could be depleted of their complement of GTP and IF 2. Such depleted initiation complexes were still able to accept 50 S subunits to form 70 S complexes which could still donate fMet tRNA into peptide linkages. These results indicate that 30 S complexes lacking GTP do not require IF 2 for formation of active 70 S complexes. IF 1, which is required to prevent dissociation of IF 2 from the 30 S initiation complex, is also required for release of IF 2 from ribosomes following 70 S initiation complex formation. The mechanism of the release of IF 2 has been studied in greater detail. Evidence is presented which rules out the presence of a stable IF 2 GDP complex on the surface of the 70 S ribosome following GTP hydrolysis and of any exchange reactions between IF 1 and guanine nucleotides necessary for effecting the release of IF 2. IF 2 remains on the 70 S initiation complexes after release of guanine nucleotides and can be liberated solely by addition of IF 1.

AB - Studies on the function of initiation factor 1 (IF 1) in the formation of 30 S initiation complexes have been carried out. IF 1 appears to prevent the dissociation of initiation factor 2 (IF 2) from the 30 S initiation complex. The factor has no effect on either the initial binding of IF 2 nor does it increase the amount of IF 2 dependent fMet tRNA and GTP bound to the 30 S subunit. Bound fMet tRNA remains stable to sucrose gradient centrifugation even in the absence of IF 1. It is postulated that the presence of IF 2 on the 30 S complex is necessary so that at the time of junction with the 50 S subunit to form a 70 S complex, the 70 S dependent GTPase activity of IF 2 can hydrolyze GTP. This hydrolysis provides a means by which GTP can be removed to facilitate formation of a 70 S initiation complex active in peptidyl transfer. In support of this postulate, it was observed that 30 S initiation complexes formed in the absence of IF 1 could be depleted of their complement of GTP and IF 2. Such depleted initiation complexes were still able to accept 50 S subunits to form 70 S complexes which could still donate fMet tRNA into peptide linkages. These results indicate that 30 S complexes lacking GTP do not require IF 2 for formation of active 70 S complexes. IF 1, which is required to prevent dissociation of IF 2 from the 30 S initiation complex, is also required for release of IF 2 from ribosomes following 70 S initiation complex formation. The mechanism of the release of IF 2 has been studied in greater detail. Evidence is presented which rules out the presence of a stable IF 2 GDP complex on the surface of the 70 S ribosome following GTP hydrolysis and of any exchange reactions between IF 1 and guanine nucleotides necessary for effecting the release of IF 2. IF 2 remains on the 70 S initiation complexes after release of guanine nucleotides and can be liberated solely by addition of IF 1.

UR - http://www.scopus.com/inward/record.url?scp=0017346649&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0017346649&partnerID=8YFLogxK

M3 - Article

VL - 252

SP - 1739

EP - 1744

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 5

ER -