var _gaq _gaq = _gaq.push (['_trackPageview']); (function () {var ga = document.createElement ('script'); ga.type = 'text / javascript'; ga.async = true; ga.src = (' https: '== document.location.protocol?' https: / / ssl ':' http://www ') +' .google-analytics.com/ga.js '; var s = document.getElementsByTagName (' script ') [0]; s.parentNode.insertBefore (ga, s); })();
Proteins consist of a set of Piau small molecules known as amino acids, a specific sequence of amino acids will ensure that the future can take a specific protein structure and function. The assemblage of various amino acids is carried out by molecular complexes known as ribosomes, the amino acid sequence formed proteins, however, are synthesized in the ribosomes simply linking to one another in sequence the various amino acids and thus initially consist of chains without a precise three-dimensional shape. Most of the protein chain wraps then spontaneously to take the final structure, the proteins tend to fold in such a way as to avoid ch nonpolar side chains of amino acids come into contact with the aqueous environment of the cell. Not all Portein can fold spontaneously, some are made up of hundreds of amino acids and must be helped to fold properly. the specific sequence of amino acids as we said it is important to allow the protena to fold into a specific shape and could take a specific functionality. If the withdrawal is not successful the feature is missing, or can be modified with deleterious consequences for the cell.
Cells can not wait passively proteins ripieghino correctly. Proteins are often incorrectly wrapped in apolar amino acids on the surface, rather than hidden in a safe in them. These non-polar hydrocarbon portions bind strongly with similar portions on other proteins and forming large aggregates. Random aggregates leading to the death cells: diseases such as sickle cell disease, mad cow disease, and Alzheimer's disease are caused by unnatural combinations of proteins that form fibrils which interfere with the cellular life.
Fortunately, the cell takes care of everything and there is a particular protein known as grppo Chaperon that guide other proteins during the process of proper folding. Protect them during the retreat shielded by other proteins that may bind and prevent the process. Many chaperone proteins are called "thermal shock" (with names such as HSP-60) because they are synthesized in large amounts when cells are exposed to strong heat, as in the case of burns. Too hot in general, destabilizes the protein and makes folding more often wrong. So when the temperature rises too much, the cells need extra help with their proteins.
The Chaperon HSP-60
This type of chaperone is complex and creates a closed environment for protein folding during which protects them completely during the process. An example is the complex GroEL- GroES of E.coli bacteria.
The structure consists of two overlapping rings of GroEL proteins, colored in green and blue, and a cap on the underside of GroES protein, colored red and yellow. As shown in the picture above, seven GroEL proteins form a ring with an internal cavity of the size of a protein. Proteins do not come wrapped up in this cavity and fold in it.
Some smaller proteins that protect the ribosome have just left. At this stage the protein can have a very small percentage of their structure already folded, so the portions of the elongated chain with groups of non-polar hydrocarbon type are particularly susceptible to aggregation. 
The chaperone HSP-70 (shown above) these portions is elongated, and there binds the fencing from the surrounding molecules. Then, with the energy of ATP, the chaperones release the chain when it is ready to fold. The HSP-70 are composed of two domains: one that binds ATP and controls the process, shown in the upper left from PDB 1dkg, and one that binds to portions of the protein chain is not wrapped in apolar hydrocarbon groups. A small peptide, colored pink, is tied in the deep cleft that binds the protein.
explore the structure
The large complex GroEL-GroES. In this figure three subunits have been removed GroEL in each ring to show the interior, leaving four subunits in each ring. In the two subunits on the back, hydrocarbon nonpolar amino acids LEU, ILE, VAL, MET, PHE, TYR and TRP are colored in blue. Note the strip of hydrocarbon hydrophobic amino acids near the entrance at the top. This interacts strongly with proteins do not fold luring them into the cavity. Now look at the lower cavity, capped by GroES in the bottom colored red. Using the energy of ATP (ADP is located in this structure, colored in red), the ring GroEL undergoes a great change in shape. The cavity becomes much larger, and the strip of hydrocarbon nonpolar amino acids is no longer in contact with the cavity. This means that a protein chain trapped inside (not shown) to close in on itself, having enough space for the process.
Sources:
PDB 
0 comments:
Post a Comment