Which cell organelle serves as the site of protein synthesis?

The best known and studied bacterial toxin is the diphtheria toxin,produced by . Diphtheria toxin is abacterialexotoxin of the A/B prototype. It is produced as single polypeptidechainwith a molecular weight of 60,000 daltons. The function of the proteinis distinguishable into two parts: subunit A, with a m.w. of 21,000daltons,contains the enzymatic activity for inhibition of elongation factor-2involvedin host protein synthesis; subunit B, with a m.w. of 39,000 daltons, isresponsible for binding to the membrane of a susceptible host cell. TheB subunit possesses a region T (translocation) domain which insertsinto the endosome membrane thus securing the release of the enzymaticcomponent into the cytoplasm.

serve as sites for protein synthesis

07/01/2010 · Which cell organelle serves as the site of protein synthesis ..

they are sites of protein synthesis in the cell; ..

are where RNA is translated into protein. This process is called protein synthesis. Protein synthesis is very important to cells, therefore large numbers of ribosomes are found in cells. Ribosomes float freely in the cytoplasm, and are also bound to the endoplasmic reticulum (ER). ER bound to ribosomes is called rough ER because the ribosomes on the ER give it a rough sandpaper like look.. These organelles are very small, made up of 50 proteins and several long RNAs bound together. Ribosomes do not have a membrane. Ribosomes fall into two seperate units while not synthesizing protein.

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These are composed of proteins and ribosomal RNA (rRNA), the most abundant RNA in the cell.

Each ribosome has a binding site for mRNA and three binding sites for tRNA molecules.

The P site holds the tRNA carrying the growing polypeptide chain.

The A site carries the tRNA with the next amino acid.

Discharged tRNAs leave the ribosome at the E site.

RNA is the catalyst for peptide bond formation.

Part B - Sites of protein synthesis All proteins are synthesized by ribosomes in the cell

This lesson will introduce protein synthesis and explain ..

Aminoacyl-tRNA synthetases (AARSs) comprise an enzyme family that generates and maintains pools of aminoacylated tRNAs, which serve as essential substrates for protein synthesis. Many protein synthesis factors, including tRNA and AARSs also have non-canonical functions. Particularly in mammalian cells, alternate functions of AARSs have been associated with re-distribution in the cell to sites that are removed from translation. Sub-fractionation methods for E. coli were designed and optimized to carefully investigate re-localization of bacterial AARSs and tRNA that might aid in conferring alternate activities. Cell fractionation included isolation of the cytoplasm, periplasm, membrane, outer membrane vesicles, and extracellular media. Specific endogenous proteins and RNAs were probed respectively within each fraction via Western blots using antibodies and by Northern blots with primers to unique regions of the nucleic acid.

Protein Synthesis Flashcards | Quizlet

There are a variety of ways that toxin subunits may be synthesizedandarranged: A + B indicates that the toxin is synthesized andsecretedas two separate protein subunits that interact at the target cellsurface;A-Bor A-5B indicates that the A and B subunits are synthesizedseparately,but associated by noncovalent bonds during secretion and binding totheirtarget; 5B indicates that the binding domain of the protein iscomposedof 5 identical subunits. A/B denotes a toxin synthesized as asinglepolypeptide, divided into A and B domains that may be separated byproteolyticcleavage.

Start studying Functions of Cell Organelles ..

Exotoxinsare usually secreted by bacteria and act at a site removed frombacterial growth. However, in some cases, exotoxins are only releasedbylysis of the bacterial cell. Exotoxins are usually proteins, minimallypolypeptides, that act enzymatically or through direct action with hostcells and stimulate a variety of host responses. Most exotoxins act attissue sites remote from the original point of bacterial invasionor growth. However, some bacterial exotoxins act at the site ofpathogen colonizationand may play a role in invasion.