Component of the 60-80S U3 small nucleolar ribonucleoprotein (U3 snoRNP). Required for the early cleavages during pre-18S ribosomal RNA processing. Homo sapiens (taxid: 9606)
>sp|Q3T0M3|IMP3_BOVIN U3 small nucleolar ribonucleoprotein protein IMP3 OS=Bos taurus GN=IMP3 PE=2 SV=1
Component of the U3 small nucleolar ribonucleoprotein. Required for the early cleavages at sites A0, A1 and A2 during 18S ribosomal pre-RNA processing.
>PF00163 Ribosomal_S4: Ribosomal protein S4/S9 N-terminal domain; InterPro: IPR001912 Ribosomes are the particles that catalyse mRNA-directed protein synthesis in all organisms
The codons of the mRNA are exposed on the ribosome to allow tRNA binding. This leads to the incorporation of amino acids into the growing polypeptide chain in accordance with the genetic information. Incoming amino acid monomers enter the ribosomal A site in the form of aminoacyl-tRNAs complexed with elongation factor Tu (EF-Tu) and GTP. The growing polypeptide chain, situated in the P site as peptidyl-tRNA, is then transferred to aminoacyl-tRNA and the new peptidyl-tRNA, extended by one residue, is translocated to the P site with the aid the elongation factor G (EF-G) and GTP as the deacylated tRNA is released from the ribosome through one or more exit sites [, ]. About 2/3 of the mass of the ribosome consists of RNA and 1/3 of protein. The proteins are named in accordance with the subunit of the ribosome which they belong to - the small (S1 to S31) and the large (L1 to L44). Usually they decorate the rRNA cores of the subunits. Many ribosomal proteins, particularly those of the large subunit, are composed of a globular, surfaced-exposed domain with long finger-like projections that extend into the rRNA core to stabilise its structure. Most of the proteins interact with multiple RNA elements, often from different domains. In the large subunit, about 1/3 of the 23S rRNA nucleotides are at least in van der Waal's contact with protein, and L22 interacts with all six domains of the 23S rRNA. Proteins S4 and S7, which initiate assembly of the 16S rRNA, are located at junctions of five and four RNA helices, respectively. In this way proteins serve to organise and stabilise the rRNA tertiary structure. While the crucial activities of decoding and peptide transfer are RNA based, proteins play an active role in functions that may have evolved to streamline the process of protein synthesis. In addition to their function in the ribosome, many ribosomal proteins have some function 'outside' the ribosome [, ]. Ribosomal protein S4 is one of the proteins from the small ribosomal subunit. S4 is known to bind directly to 16S ribosomal RNA. The crystal structure of a bacterial S4 protein revealed a two domain molecule. The first domain is composed of four helices in the known structure. The second domain is an insertion within domain 1 and displays some structural homology with the ETS DNA binding domain []. This entry represents the domain found at the N terminus of small ribosomal subunits S4 and S9. ; GO: 0019843 rRNA binding, 0005622 intracellular; PDB: 3BBN_D 2WWL_D 3OR9_D 3OFA_D 2QBB_D 3OFP_D 4A2I_D 2QB9_D 3OFO_D 2QBF_D ....
