Central Dogma from gene to protein 2

37問 • 1年前

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Amino acid activation by synthetase enzymes aminoacyl-RNA synthetases

Aminoacyl-tRNA synthetases attach the correct amino acid to its corresponding tRNA using ATP, ensuring accurate protein creation, tRNA molecule has an anticodon that binds to the complementary codon on mRNA, ensuring the correct amino acid is added to the growing polypeptide chain.

Amino acid activation by synthetase enzymes

* Amino acid binds to synthetase tRNA. * ATP provides energy for activation * tRNA binds to its codon in RNA * Amino acid is selected by it's codon

The incorporation of an amino acid into a protein

formation of a peptide bond between the carboxyl group at the end of a growing polypeptide chain and a free amino group on an incoming amino acid

Polysomes

are multiple ribosomes translating the same mRNA molecule simultaneously

Ribosmes

are protein-making machines

bacterial and eukaryotic ribosomes

Eukaryotic ribosomes (80S) are larger than bacterial ribosomes (70S) and differ in subunit composition.

The 'S' value refers

To measures how fast a particle settles in a centrifuge.

The RNA-binding sites in the ribosome How many subunits

It has 2 subunits(small & large)

The RNA-binding sites in the ribosome When ribosome isn't making proteins

ribosome subunits are separate. They join on an mRNA molecule to start protein creation

The RNA-binding sites in the ribosome What and How many types of binding sites for RNA

4 binding sites for RNA 1 for mRNA and 3 types of tRNA: A, P, and E sites.

Translation

the process of converting genetic information from mRNA into proteins.

Translating an mRNA molecule

* Initiation: Ribosome binds to mRNA, first tRNA binds. * Elongation: tRNA carrying amino acids binds to A site, peptide bond forms, tRNAs shift. * Termination: Stop codon reached, protein released

The initiation of protein synthesis in eukaryotes

* Small subunit binds mRNA. * Initiator tRNA binds. * Large subunit joins. * Peptide bond forms.

structures of prokaryotic and eukaryotic mRNA molecules

Prokaryotic mRNA: * Multiple start sites (ribosome-binding sites) * Can produce multiple proteins from one mRNA Eukaryotic mRNA: * Single start site (AUG codon) * Typically produces one protein per mRNA

Release Factor

bind to ribosome with stop codons at A site and add water to the polypeptide chain, releasing it.

The final phase of protein synthesis

* Stop Codon: Ribosome reaches a stop codon (UAA, UAG, UGA). * Release Factor: Binds to the stop codon at A site * Peptide Release: Water molecule added,breaking bond between polypeptide and tRNA in p site * Dissociation: Ribosome, mRNA, and tRNAs separate.

Polyribosome

is a cluster of ribosomes translating the same mRNA, allowing for efficient protein production.

Nonsense-Mediated mRNA Decay (NMD)

quality control mechanism that degrades mRNAs with premature stop codons.occurs when ribosome encounters a stop codon before removing all (EJCs) from mRNA.presence of EJCs signals the mRNA for degradation, preventing the production of faulty proteins.

Protein Folding and Maturation

* Newly created polypeptide chains fold into 3D structures. * Covalent modifications (e.g., phosphorylation, glycosylation) can occur. * Proteins can bind to other proteins to form complexes. * The final, correctly folded and modified protein is functional.

Co-translational Protein Folding

* Nascent Chain Folding: As polypeptide chain emerges from the ribosome, it starts to fold. * Domain Formation:N-terminal domain folds first, then the C-terminal domain. * Final Folding: The entire chain undergoes final folding to form the functional protein after release from ribosome

Molecular Chaperones

* Assist in protein folding. * Prevent misfolding. * Use ATP energy to refold or degrade misfolded proteins.

Hsp60 Chaperonin

* Misfolded protein binds to Hsp60. * GroES cap encloses the protein. * ATP breaking powers folding. * Correctly folded protein is released.

Proteasome

* Degrades unwanted proteins. * Recognizes proteins tagged with ubiquitin. * Unfolds and breaks down proteins into peptides.

Structure of the proteasome

proteasome cap recognizes proteins marked for degradation with a polyubiquitin chain. It uses a ubiquitin receptor to bind the chain, then removes it with a ubiquitin hydrolase. The unfolded protein is then sent to the unfoldase ring for recycling.

Activation of a specific E3 molecule Phosphorylation by protein kinase

A phosphate group activates the E3 ligase

Activation of a specific E3 molecule Allosteric transition caused by ligand binding

A ligand molecule binds and activates the E3 ligase

Activation of a specific E3 molecule Allosteric transition caused by protein subunit addition

A protein subunit binds and activates the E3 ligase

Degradation signal exposure in the protein to be degraded Phosphorylation by protein kinase

Adding a phosphate group signals degradation.

Degradation signal exposure in the protein to be degraded * Unmasking by protein dissociation :

Removing a protein subunit exposes a degradation signal.

Degradation signal exposure in the protein to be degraded * Destabilizing N-terminus:

Creating a new N-terminus triggers degradation

gene expressiongene expression Transcription

DNA is copied into a (mRNA) molecule. This mRNA contains both (exons) and (introns) regions

gene expression RNA Processing

The introns are removed from the mRNA, and a 5' cap and a poly-A tail are added. This mature mRNA is ready for translation

gene expression Translation

The mRNA is read by ribosomes, which translate the genetic code into a protein sequence

Transcription Start Site (TSS):

The point where transcription begins

* 5' Untranslated Region (5' UTR):

The region before the coding sequence

Coding Sequence (CDS):

The region that codes for the protein

* 3' Untranslated Region (3' UTR):

The region after the coding sequence

cell biology

kiler · 16問 · 1年前

cell biology