Thursday, January 29, 2015
Proteins involved in the biosynthesis of proteins.
Proteins need to be polymerized, folded and covalently modified in a number of ways. Lets discuss the type of proteins that are needed for these processes. Think about what problems the cell needs to solve to produce biologically active structure. Start with the ribosome. and those proteins involved with peptide bond formation.
Subscribe to:
Post Comments (Atom)
After refreshing my memory on translation via wikipedia, it seems enzymes and initiation factors are the type of proteins immediately involved with protein synthesis. These initiation factors both exist in eukaryotes and prokaryotes and complex to aid in the interaction between the ribosome and the mRNA being translated. Then enzymes (aminoacyl tRNA synthase) attach amino acids corresponding to the mRNA onto tRNA's which position the amino acids in a manner in which peptide bonds form through biochemical interactions. However, another set of proteins, elongation factors, aid in the forming of these peptide bonds.
ReplyDeleteAfter these polypeptide chains are created, they may still not be biologically active. For example, proinsulin (a precursor to insulin) must be cleaved (proteases) to become biologically active insulin.
There are also regulatory proteins involved in the process to make sure only properly structured/functional proteins "get through" For example, ubiquitin is a protein that may be attached to an improperly folded polypeptide chain and signal for its degradation before it leaves the cell.
Just from these examples alone you can see there needs to be proteins for regulation, folding, communicating, transportation, and postranslational mods like glycosylation. So many classes of proteins have to work together to create a single active protein.
http://en.wikipedia.org/wiki/Protein_biosynthesis
DeleteHistone protein is one of the example.Histone,the nucleosome and DNA form the fundamental building blocks of eukaryotic chromatin which are the diverse array of post-translational modifiers that often occur on tail domain.Modification of one or more tail act sequentially or in a combination to form a histone code that is read by other protein to bring about distinct downstream.
ReplyDeleteThere are several events and protein interactions occurring in the ER and golgi in order to produce post-translational modification for a functional protein product.
ReplyDeleteFor example, isomerases alter the chemical chirality and isomer conformation of amino acids ultimately leading to changes in the overall conformation of a protein. These steric exchanges may even precede and result in the formation of covalent interactions such as disulphide bridges.
Additionally, chaperone proteins facilitate the formation of macromolecular structures while also preventing misfolding especially in response to extreme environmental conditions. Proper folding can be absolutely detrimental for cell health. For instance protein aggregation (a process normally prevented by chaperone proteins) can be seen in degenerative diseases such as Alzheimer’s. While it is not certain if these aggregates are a cause or product of disease onset, there are several other diseases including emphysema, cystic fibrosis, and sickle cell which are directly caused by inappropriate protein conformation.
Post-translational phosphorylation, which requires a number of kinases, is absolutely essential for proteins to be properly regulated in their functioning. Despite proteins being engineered through translation, the addition of phosphate groups ensures that their functions, including those required for cell cycle process, apoptosis and cell growth, are carried out at the proper time and to the proper extent.
ReplyDeleteThis topic makes me think of the teams of proteins that are often required to synthesize proteins as they become increasingly complex. An example of this is glutathione, which requires two separate enzymes to fully synthesize its completed, tripeptide formation. These type of enzymes can often be highly specific for certain peptides. With the above example, the enzymes creating glutathione are gamma-glutamylcysteine synthetase and glutathione synthetase.
ReplyDelete