title: Studies on the function of two adjacent N6,N6-dimethyladenosines near the 3' end of 16 S ribosomal RNA of Escherichia coli. II. The effect of the absence of the methyl groups on initiation of protein biosynthesis.
abstract: The effect of the presence or absence of methyl groups on the N6 atoms of two adjacent adenosines near the 3' end of 16 S rTNA of Escherichia coli on initiation of protein biosynthesis has been studied using wild type (methylated) and kasugamycin-resistant (unmethylated) E. coli ribosomes (see preceding paper (Poldermans, B., Goosen, N., and Van Knippenberg, P. H. (1979) J. Biol. Chem. 254, 9085--9089)). Conditions of pH, temperature, and ionic strength at which binding of fMet-tRNA to ribosomes proceeds maximally are the same for wild type and mutant ribosomes. Mg2+- and factor-dependent dissociation of ribosomes as well as the association of the subunits is also the same for methylated and unmethylated ribosomes. Binding of fMet-tRNA to wild type and to mutant 70 S ribosomes requires the same amount of the three initiation factors. However, optimal fMet-tRNA binding to unmethylated 30 S ribosomes needs more of initiation factor 3 than does binding to methylated 30 S ribosomes, provided that initiation factor 1 is absent. This difference is completely abolished when mutant 30 S ribosomes are methylated using purified methylase from the wild type strain and the methyl donor S-adenosylmethionine.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives*; D004926:Escherichia coli / Q000378:metabolism*; D007700:Kinetics; D009154:Mutation; D010442:Peptide Chain Initiation, Translational; D010448:Peptide Initiation Factors / Q000378:metabolism*; D012315:RNA Caps / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D013045:Species Specificity
chemical_list: D010448:Peptide Initiation Factors; D012315:RNA Caps; D012335:RNA, Ribosomal; D012346:RNA, Transfer, Amino Acyl; D000241:Adenosine