Biomaterial Database

Interaction of bacterial initiation factor 2 with initiator tRNA. 1976

R M Sundari, and E A Stringer, and L H Schulman, and U Maitra

Interaction of bacterial polypeptide chain initiation factor 2 (IF-2) with Escherichia coli formylmethionyl-tRNA in the absence of free Mg2+ renders the fMet-tRNA adsorable to nitrocellulose membrane filters. This reaction does not require GTP and is strongly inhibited by low concentration (1 mM) of Mg2+ in the reaction mixture. The structural requirements of the tRNA for binary complex formation have been studied using modified fMet-tRNAfMet molecules and a series of N-blocked and normal aminoacyl-rRNAs. It has been observed that IF-2 will not blind either to free formylmethionine or to a short fMet-oligonucleotide, but will bind to any xRNA structure covalently attached to an N-blocked methionine group. The E. coli initiator and noninitiator methiionine tRNAs, which have many differences in primary structure, were found to bind identically. In addition, fMet-tRNAfMet molecules containing structural modidifications at 20 different sites had the same affinity for IF-2 as unmodified fMet-tRNAfMet. N-blocked eukaryotic initiator tRNAs were also found to bind strongly to the factor. Binary complex formation was readily reversible, f[14C]Met-tRNAfMet being competed out by addition of an equal amount of unlabeled fMet-tRNAfMet to the preformed complex. In contrast, deacylated tRNAfMet was a poor compeitor, a 30-fold excess being required for 50% inhibition of complex formation in the presence of limiting factor. Although tRNAs having an N-blocked methionine were found to have the greatest affinity for IF-2, specificity for the amino acid in binary complex formation was not absolute. Partial binding was observed with N-substituted tyrosine, valine, and phenylalanine tRNAs, and weak or no binding with N-subsituted lysine, alanine, and leucine tRNAs. In all cases, N-blocked derivatives had a higher affinity for IF-2 than the corresponding unsubstituted aminoacyl-tRNAs. These results indicate that IF-2 alone is not capable of distinguishing the nucleotide sequence of tRNAs and selects the initiator tRNA by recognizing the fMet moiety. The overall data suggest that the role of IF-2 in formation of the ribosomal initiation complex is to stablize the interaction of fMet-tRNAfMet with the ribosome at low Mg2+ concentrations by binding to both the ribosomal particle and the fMet group of the tRNA.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008274	Magnesium	A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D008715	Methionine	A sulfur-containing essential L-amino acid that is important in many body functions.	L-Methionine,Liquimeth,Methionine, L-Isomer,Pedameth,L-Isomer Methionine,Methionine, L Isomer
D010445	Peptide Elongation Factors	Protein factors uniquely required during the elongation phase of protein synthesis.	Elongation Factor,Elongation Factors, Peptide,Factor, Elongation,Factors, Peptide Elongation
D010448	Peptide Initiation Factors	Protein factors uniquely required during the initiation phase of protein synthesis in GENETIC TRANSLATION.	Initiation Factors,Initiation Factor,Factors, Peptide Initiation,Initiation Factors, Peptide
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D004926	Escherichia coli	A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.	Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D006160	Guanosine Triphosphate	Guanosine 5'-(tetrahydrogen triphosphate). A guanine nucleotide containing three phosphate groups esterified to the sugar moiety.	GTP,Triphosphate, Guanosine
D000604	Amino Acyl-tRNA Synthetases	A subclass of enzymes that aminoacylate AMINO ACID-SPECIFIC TRANSFER RNA with their corresponding AMINO ACIDS.	Amino Acyl T RNA Synthetases,Amino Acyl-tRNA Ligases,Aminoacyl Transfer RNA Synthetase,Aminoacyl-tRNA Synthetase,Transfer RNA Synthetase,tRNA Synthetase,Acyl-tRNA Ligases, Amino,Acyl-tRNA Synthetases, Amino,Amino Acyl tRNA Ligases,Amino Acyl tRNA Synthetases,Aminoacyl tRNA Synthetase,Ligases, Amino Acyl-tRNA,RNA Synthetase, Transfer,Synthetase, Aminoacyl-tRNA,Synthetase, Transfer RNA,Synthetase, tRNA,Synthetases, Amino Acyl-tRNA
D000641	Ammonia	A colorless alkaline gas. It is formed in the body during decomposition of organic materials during a large number of metabolically important reactions. Note that the aqueous form of ammonia is referred to as AMMONIUM HYDROXIDE.