Open AccessFurther Studies with Labelled Polypeptide‐Chain‐Initiation Factor 3 (IF‐3)
Author(s) -
Sabol Steven,
Meier Dankwart,
Ochoa Severo
Publication year - 1973
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1973.tb02687.x
Subject(s) - ribosome , ribosomal rna , 50s , ribosomal protein , biochemistry , initiation factor , chemistry , escherichia coli , rna , stereochemistry , biology , gene
The preparation of 35 S‐labelled initiation factor 3 (IF‐3) from Escherichia coli is described. As reported earlier, labelled IF‐3 binds to 30‐S, but not to 50‐S ribosomal subunits or 70‐S ribosomes, and is released upon formation of a 70‐S couple. In continuation of this work we find that the 30‐S binding of IF‐3 is rather sensitive to aurin‐tricarboxylic acid, a powerful inhibitor of polypeptide chain initiation, but relatively insensitive to streptomycin. IF‐3 binds weakly to both 23‐S and 16‐S ribosomal RNA and to 23‐S but not 43‐S ribosomal cores, Free IF‐3 readily exchanges with the 30‐S‐bound factor even at low temperature. There is also an exchange of 50‐S or 30‐S ribosomal subunits labelled with [ 3 H]uracil into 70‐S ribosomes in the absence of the reactions of protein synthesis. This exchange is markedly temperature‐dependent and strongly inhibited at high (20 mM) Mg 2+ concentrations.