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A ribosomal protein (r-protein or rProtein [1] [2] [3]) is any of the proteins that, in conjunction with rRNA, make up the ribosomal subunits involved in the cellular process of translation. E. coli , other bacteria and Archaea have a 30S small subunit and a 50S large subunit, whereas humans and yeasts have a 40S small subunit and a 60S large ...
Prokaryotic ribosomes begin translation of the mRNA transcript while DNA is still being transcribed. Thus translation and transcription are parallel processes. Bacterial mRNA are usually polycistronic and contain multiple ribosome binding sites. Translation initiation is the most highly regulated step of protein synthesis in prokaryotes. [5]
These proteins bind the small (40S) ribosomal subunit and hold the mRNA in place. [1] eIF3 is associated with the 40S ribosomal subunit and plays a role in keeping the large (60S) ribosomal subunit from prematurely binding. eIF3 also interacts with the eIF4F complex, which consists of three other initiation factors: eIF4A, eIF4E, and eIF4G.
The ribosomal proteins and rRNAs are arranged into two distinct ribosomal pieces of different sizes, known generally as the large and small subunits of the ribosome. Ribosomes consist of two subunits that fit together and work as one to translate the mRNA into a polypeptide chain during protein synthesis.
The ribosomal P-site plays a vital role in all phases of translation. Initiation involves recognition of the start codon (AUG) by initiator tRNA in the P-site, elongation involves passage of many elongator tRNAs through the P site, termination involves hydrolysis of the mature polypeptide from tRNA bound to the P-site, and ribosome recycling involves release of deacylated tRNA.
The B protein is typically referred to as the dehydrogenase; the C and D proteins together form the cyclodehydratase, although the D protein alone performs the cyclodehydration reaction. Early work on microcin B17 adopted a different nomenclature for these proteins, but a recent consensus has been adopted by the field as described above.
The A-site (A for aminoacyl) of a ribosome is a binding site for charged t-RNA molecules during protein synthesis. [1] One of three such binding sites, the A-site is the first location the t-RNA binds during the protein synthesis process, the other two sites being P-site (peptidyl) and E-site (exit).
The alpha operon ribosome binding site in bacteria is surrounded by this complex pseudoknotted RNA structure. Translation of the mRNA produces 4 ribosomal protein products, one of which (S4) acts as a translational repressor by binding to the nested pseudoknot region.