Proteins of the 30-S subunit of Escherichia coli ribosomes which interact directly with natural mRNA.

Ultraviolet irradiation (254 nm) of the complexes of MS2 phage RNA (mRNA) and the 30-S subunits of Escherichia coli ribosomes prepared at 0 degrees C and 37 degrees C in the presence and absence of initiation factor 3 (IF-3) causes cross-linking of mRNA with proteins S3, S4, S5, S7, S9, S18 and IF-3. Hence, these proteins interact directly with mRNA within the complex 30-S-subunit . mRNA.

Polynucleotide-protein interactions in the translation system. Detection of contacts between some ribosomal split proteins and 16-S RNA in 30-S subunits of Escherichia coli ribosomes.

Direct contacts between 16-S RNA and split proteins S2, S3, S5, S14 and S21 inside the 30-S subunit of Escherichia coli ribosomes were evidenced by the formation of ultraviolet-induced (lambda = 254 nm) RNA-protein cross-links. 30-S subunits were reassembled from core particles and a mixture of split proteins containing in each case a single 125I-labelled protein. All the proteins tested are cross-linked as a result of a single-hit process; proteins S3 and S21 were cross-linked at the highest rate.