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Newly synthesized integral proteins are guided to the membrane by signal sequences that target them to the endoplasmic reticulum (ER). Once at the ER, the proteins are translocated across the membrane through a channel formed by the translocon complex. The hydrophobic regions of the protein interact with the lipid bilayer, while the hydrophilic regions remain exposed to the aqueous environment, resulting in the protein being inserted into the membrane.
1 answer
-Some proteins are targeted to the ER by a signal sequence which is recognised by an SRP (signal recognition particle). The protein is translated into the ER through the translocon.
Modifications:
-Signal sequence is cleaved by a signal transpeptidase.
-Protein folding is aided by molecular chaperones such as BiP and Calnexin.
-O linked and N linked glycosylation occurs (N-linked most common).
-Di sulfide bond formation occurs (highly reducing environment inside the ER unlike in the cytoplasm)
- GPI anchor modifications
-ubiquitination - and then proteins can be degraded by the proteosome in the cytosol. Occurs if protein is not folded correctly. The unfolded response can also occur.
1 answer
G protein-coupled receptors (GPCRs) are made through a process called protein synthesis. The gene encoding the GPCR is transcribed into mRNA, which is then translated by ribosomes in the cell to produce the GPCR protein. The protein is then properly folded and modified in the endoplasmic reticulum and Golgi apparatus before being transported to the cell membrane where it can interact with G proteins.
2 answers
Proteins that move to the nucleus do not require an N-terminal signal peptide because nuclear localization signals within the protein sequence direct them to the nucleus. These signals are recognized by nuclear transport proteins, which facilitate the proteins' transport through nuclear pores.
2 answers
RNA has lots of functions.
mRNA - messenger RNA - is a "copy" of the DNA base sequence of a gene after processing (capping, addition of 3' tail and splicing). It is used to transfer the genetic information from DNA, which is a storage molecule and quite inaccessible, to ribosomes, which perform translation to synthesise polypeptides.
tRNA - transfer RNA - is "charged" with an amino acid and used to recognize the code in the mRNA and "translate" it into the amino acid it is carrying. There are specific tRNA molecules for each amino acid.
rRNA - Ribosomal ribonucleic acid is the RNA component of the ribosome, the protein manufacturing machinery of all living cells. Ribosomal RNA provides a mechanism for decoding mRNA intoamino acids and interacts with tRNAs during translation by providing peptidyl transferase activity. The tRNAs bring the necessary amino acids corresponding to the appropriate mRNA codon.
snRNA - small nuclear RNA - regulates and provides the catalytic machinery for splicing or mRNA.
gRNA - guide RNA - directs editing of RNA to specific sites.
miRNA - micro RNA - inhibits translation by base pairing with complementary sequences of mRNA.
Signal Recognition Particle - RNA/protein molecule that binds to the "Signal Sequence" on polypeptides to be sent to the endoplasmic reticulum, causing translation to pause until polypeptide has been fed into translocon for entry into ER.
There are others too....
RNA is a nucleic acid involved in protein synthesis. In some organisms it is also responsible for carrying the genetic code.
mRNA carries a copy of the instructions from the DNA in the nucleus to the ribosomes.
rRNA is a major component of ribosomes - the site of protein synthesis.
tRNA carries the amino acids which are added to the polypeptide chain (protein) being synthesized. It helps copy DNA and transfer it to other cells.
1 answer
RNA has lots of functions.
mRNA - messenger RNA - is a "copy" of the DNA base sequence of a gene after processing (capping, addition of 3' tail and splicing). It is used to transfer the genetic information from DNA, which is a storage molecule and quite inaccessible, to ribosomes, which perform translation to synthesise polypeptides.
tRNA - transfer RNA - is "charged" with an amino acid and used to recognize the code in the mRNA and "translate" it into the amino acid it is carrying. There are specific tRNA molecules for each amino acid.
rRNA - Ribosomal ribonucleic acid is the RNA component of the ribosome, the protein manufacturing machinery of all living cells. Ribosomal RNA provides a mechanism for decoding mRNA intoamino acids and interacts with tRNAs during translation by providing peptidyl transferase activity. The tRNAs bring the necessary amino acids corresponding to the appropriate mRNA codon.
snRNA - small nuclear RNA - regulates and provides the catalytic machinery for splicing or mRNA.
gRNA - guide RNA - directs editing of RNA to specific sites.
miRNA - micro RNA - inhibits translation by base pairing with complementary sequences of mRNA.
Signal Recognition Particle - RNA/protein molecule that binds to the "Signal Sequence" on polypeptides to be sent to the endoplasmic reticulum, causing translation to pause until polypeptide has been fed into translocon for entry into ER.
There are others too....
RNA is a nucleic acid involved in protein synthesis. In some organisms it is also responsible for carrying the genetic code.
mRNA carries a copy of the instructions from the DNA in the nucleus to the ribosomes.
rRNA is a major component of ribosomes - the site of protein synthesis.
tRNA carries the amino acids which are added to the polypeptide chain (protein) being synthesized. It helps copy DNA and transfer it to other cells.
5 answers
