Ribosomal Protein S1 Associates with Escherichia coli Ribosomal 30‐S Subunit by Means of Protein‐Protein Interactions

Abstract

Ribosomal proteins S1 when associated with the 3 0 3 subunit does not interact with 16-S RNA but its binding is determined mostly by protein-protein interactions. These conclusions are based on the following data.1. Ultraviolet irradiation (1. = 254 nm) of the 30-S subunit does not result in the covalent cross-linking of S1 with 16-S RNA at irradiation doses up to 150 quanta/nucleotide, whereas the irradiation under the same conditions of S1 . polynucleotide complexes [Sl . poly(U), S1 . poly(A) and S1 . Qfl phage RNA] induces effective formation of polynucleotide-protein cross-links.2. Mild treatment of 30-S subunits lacking S-I with RNase A or with cobra venom endonuclease results in removal of 10-20% of the total nucleotide material but does not affect their sedimentation characteristics or their S1 binding capacity.3. The association of S1 with S1-depleted 30-S subunits is insensitive to aurintricarboxc\lic acid, which is known as a strong inhibitor of complex formation between S1 and polynucleotides.4. Mild trypsin treatment of S1-depleted 30-S subunits greatly reduces their S 1 binding capacity.Ribosomal protein S1 is well known to be cssential for the binding of natural mRNAs by the 30-S ribosomal subunit during the first steps of protein synthesis [l -71. The molecular aspects of S1 involvement in this process are a matter for discussion. Obviously, this problem can not be resolved until the components directly interacting with S1, both in the free 30-S subunit and in initiation complexes, have been identified. The importance of RNA-binding and RNA-melting properties of S1 for its functioning is well documented now 17-111 but the question is which RNA (16-S RNA, mRNA or both of them) directly interacts with S1 during the initiation process. The present hypotheses consider all these possibilities [4,11,12]. Thus, according to the hypothesis of Dahlberg and Dahlberg [12], S1 binds to 3'-terminal region of 16-S RNA thereby Facilitating Shine-Dalgarno interactions between this region and initiation sites of mRNA [13].Howevcr, it has recently been shown that removal of the 3'-terminal fragment of 16-S RNA does not affect the ability of the 3 0 3 subunit to bind S1 [14]. On the other hand, the importance of some 30-S ribosomal proteins for S1 binding has been demonstrated [15]. These results suggest that the association of S1 with the 30-S subunit is determined by its interactions with soinelhing other than the 3'-terminal region(s) of 16-S RNA (if at all) and/or with ribosomal proteins. Another model of S1 functioning, proposed by van Dieijen et al. [4], suggests the direct involvement of S1 in mRNA recognition and binding by the 30-S subunit. This model is also supported by finding that the RNA-melting properties of S1 are not needed for its binding with the 30-S subunit but are necessary for the ability of the latter to bind natural mRNA [7]. Nevertheless the participation of interactions between 1 6 3 RNA and S1 in S1 binding cannot be The data presented below provide evidence that the association of prot...

Visualization of protein S1 within the 30S ribosomal subunit and its interaction with messenger RNA

“…We found the location by comparing the 30S subunit portion of that map, which contains S1, with the x-ray map of the S1-depleted T. thermophilus 30S subunit (25). The position derived from this study is consistent with results from IEM (17,18,19), neutron scattering (11,20,21), and S1-rRNA crosslinking (22) experiments, and it helps to explain all existing biochemical data (27,28). Our study shows that S1 is an elongated structure that makes several contacts with components of head, platform, and main body of the 30S subunit.…”

Direct Interaction of the N-Terminal Domain of Ribosomal Protein S1 with Protein S2 in Escherichia coli

“…Almost 30 years ago, it has been suggested that protein S1 associates with the 30 S ribosomal subunit by means of protein-protein interaction [32] mediated by the two N-terminal domains of S1 [12], [33]. Previous biochemical studies and cross-linking experiments indicated that protein S1 is located in spatial proximity to proteins S2, S10, and S18 [20], [21].…”

Requirements for ribosomal protein S1 for translation initiation of mRNAs with and without a 5′ leader sequence

“…Although previous work in several laboratories (van Dieijen et al, 1975;Draper et al, 1977;Boni et al, 1982;Suryanarayana and Subramanian, 1983;Roberts and Rabinowitz, 1989) clearly implicated a role for ribosomal protein S1 in mRNA recognition, direct physical evidence for S1 binding sites upstream of the RBS has only been provided more recently (Boni et al, 1991). Boni et al (1991) suggested a model in which S1 binding to single-stranded regions upstream of the RBS assists in the positioning of the TIR in the decoding site of the ribosome.…”