Heteronuclear NMR studies of E. coli translation initiation factor IF3. Evidence that the inter-domain region is disordered in solution.
Initiation factor IF3 from Escherichia coli plays a critical role in the selection of the correct initiation codon. This protein is composed of two domains, connected by a lysin-rich hydrophilic linker. The conformation of native IF3 was investigated by heteronuclear NMR spectroscopy. The two domains are independent and show little or no interaction. Heteronuclear relaxation studies of a sample selectively labelled on lysine residues demonstrates that the inter-domain linker is highly flexible, exhibiting increased 15N T2 values and negative 1H[15N] nuclear Overhause effects over a length of at least eight residues. Analysis of the rotational correlation times further shows that the motions of the two domains are most likely uncorrelated. The inter-domain linker thus displays almost totally unrestricted motions. Accordingly, the amide protons in the central region are shown to be in fast exchange with water. Such a high degree of flexibility of the inter-domain linker might be required for IF3 domains to interact with distant regions of the ribosome.
Moreau
M
M
Laboratoire de Synthèse Organique, URA 1308 du CNRS Ecole Polytechnique, Palaiseau, France.
de Cock
E
E
Fortier
P L
PL
Garcia
C
C
Albaret
C
C
Blanquet
S
S
Lallemand
J Y
JY
Dardel
F
F
D001426:Bacterial Proteins / Q000737:chemistry; D003198:Computer Simulation; D004926:Escherichia coli / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008961:Models, Structural; D009587:Nitrogen Isotopes; D010448:Peptide Initiation Factors / Q000737:chemistry* / Q000378:metabolism; D039665:Prokaryotic Initiation Factor-3; D011487:Protein Conformation; D012270:Ribosomes / Q000378:metabolism; D012996:Solutions
D001426:Bacterial Proteins; D009587:Nitrogen Isotopes; D010448:Peptide Initiation Factors; D039665:Prokaryotic Initiation Factor-3; D012996:Solutions