S1
There is not much information yet known about protein S1. Scientists do know that the RNA binding domain is at the C-terminal end of the protein. This end may be necessary for autoregulation of the ribosome (Boni et al 2000). Using mobility assay, scientists discovered that S1 worked with elongation factor EF-TU and protein SmpB, to regulate the tmRNA binding to ribosomes and to regulate the formation of free tmRNA complexes (Wower et al 2000).

S4
The structure of S4 was determined by multidimensional heteronucleaar nuclear magnetic resonance spectroscopy. S4 is made up of two globular domains; domain one consists of four alpha helices, and domain two consists of one five stranded antiparallel beta-sheet with three alpha helices packed on one side.” Domain two is located within domain one (Markus et al 1998). The crystal structure of protein shows that S4 has an extended amino terminal chain. The extension enables proteins to interact with 16S rRNA. S4 Delta 41, which consists of nucleotides 43-200 in Bacillus steearothermophilus, binds specifically to 16S rRNA and the alpha operon mRNA’s pseudoknot (Markus et al 1998). S4 binds to the 5’ domain of the 16S rRNA. It is important in the assembly of the body of the ribosome.

S7
From a two-wavelength diffraction experiment that used LIII edge of mercury, the crystal structure at 1.9 A of Thermus thermophilus was determined. S7 is made up of a beta hairpin extended between helices three and four in a cluster of six alpha helices. There are believed to be several RNA-binding sites along its surface. Helices one, four and six, and the beta-hairpin make a positively charged curved surface which is perfect for binding double-stranded RNA (Wimberly, White, and Ramakrishnan, 1997). At 2.5A resolution, an experiment was done using multiwavelength diffraction with selenomethionyl-substituted proteins. The crystallization revealed that there was a hydrophobic core with beta-sheets extending from the core. The core is made up of several helix-turn-helix motifs. Basic and aromatic amino acid residues are located on one side of the S7 protein, which is where the RNA-binding sites are believed to be located. S7 is located in the head of the 30S subunit. There it initiates assembly of the head of the 30S subunit. S7 is involved in the cross-linking of tRNA. (Hosaka et al 1997). S7 is also required for the folding of the 3’ domain of 16S rRNA and it binds to its own mRNA to regulate its own synthesis (Wimberly, White, and Ramakrishnan, 1997).

S8
Using NMR spectroscopy, the structure of protein S8 in Escherichia coli was determined. Protein S8 consists of two domains of helical segments, two RNA-binding sites, one of which is located from G588 to G604 nucleotides and the other from C634 to C651 nucleotides. There is also a hydrophobic core, which contains nine amino acid residues and is possibly associated with protein S5. Within the core is a triple base pair, nucleotides A595 x (A596 x U644). S8 plays a role in translation regulation of ribosomal proteins. The protein S8 also interacts with spc operon mRNA. Through this interaction, S8 is able to play a key role in the regulation of translation for several other ribosomal proteins (Kalurachchi et al 1997). S8 is an important RNA-binding component. It independently binds to 16S rRNA. In Escherichia coli, S8 is able to bind to its own mRNA and then regulate translation by acting as a repressor (Nevskaya et all 1998). S8 is required for the proper folding of the central domain of 16S rRNA. S8 also binds to mRNA enabling it to control the synthesis of other ribosomal proteins (Davies, Ramakrishnan, and White, 1996).