pascatranslasi processing of proteins is an important component in genome expression lines

Translation is not the end point genome expression. Polypeptide translation results are not directly active. To become active or functional protein within the cell, proteins must be processed at, Äêkurang one of the following four types of processing:
1. Protein folding (protein folding)
Polypeptide is folded into the correct tertiary structure
2. Proteolytic cleavage (proteolytic cutting)
Withholding of proteins by these proteases can remove segments, Äêsegmen from one or both ends
polypeptide. The result of cutting can be a more active protein fragment or become pendekf
fragments, Äêfragmen proteins that all or some of the active protein fragments.
3. Chemical modification (chemical modification)
Amino acid polypeptide modified through the addition of a new chemical group.
4. Intein splicing (intein removal)
Intein is Interrupt sequence in some proteins, like introns in the mRNA. Intein should be discarded
(Splicing) and exteins spliced into active proteins.
Seingkali type, different processing Äêtipe occur together, Äêsama, the polypeptide is cut, modified and / or splicing, and folded at the same time to form the correct three-dimensional conformation. In addition, the process of cutting or chemical modification may also occur after the protein is folded, this process may be as part of regulatory mechanisms of protein folding engkonversi inactive into active form.

Explain in outline the essential features of protein folding, proteolytic processing of proteins through cutting and chemical modification, and splicing intein?

Protein Folding
Not all the folding of proteins occurs spontaneously in a test tube. Proteins are small,
such as ribonuclease, can fold spontaneously when denaturan (urea) are removed.
However, large proteins can not fold spontaneously. Two factors that prevent spontaneous folding of large proteins, namely: first, the tendency to form insoluble agragrat
when denaturan omitted; second, protein tends to make folding paths that are not appropriate.
Inside the cell, protein folding is assisted by molecular chaperones.
Molecular chaperones in E. coli can be divided into two groups:
, Ä ¢ Hsp70 chaperones, which include proteins, Äêprotein Hsp70 (which is encoded by the gene dnaK) and sometimes also called DnaK protein, Hsp40 (encoded olehdnaJ) and GrpE.
, Ä ¢ Chaperonins, for example complex GroEL / GroES in E. coli.

Cutting Through proteolytic processing of protein
Cutting proteolytic have two functions in post-translational processing, namely:
1. Used to remove the short piece from the tip of the N and or C of the polypeptide, leaving a short single molecule that folds into active protein
2. Used to cut poliprotein be a part, Äêbagian with all or some of them are active potein.

Processing with chemical modification
Type the simplest chemical modification involves the addition of small chemical groups (such as an acetyl, metal or phosphate groups) to the amino acid side chains, or carboxyl group of amino acids at the end of the polypeptide. More than 150 modified amino acids have been documented in different proteins, with any modifications carried out in a very special, the same amino acids modified in the same way in each coffee protein.
A more complex type of modification is glikolisasi, sticking a large carbohydrate side chains to the polypeptide. There are two general types glikolisasi,:
1. Glikolisasi adrift O is sticking through the sugar side chain hydroxyl group of a serine or an amino threonin Asama.
2. Glikolisasi adrift N involves sticking through the side chain amino group aspargin.
Intein splicing
Last type of post-translational processing is splicing intein, which is a version protin of spicing the more extensive intron that occurs in pre RNA. Intein is part of the protein are removed immediately after translation, two external parts or ekstein then combined together.
Source: TA genomes BROWN (2002)