Protein Structure and Translation Flashcards
Transcription occurs in the
Nucleus
Primary Structure (Protein)
Amino Acid chain and order
Amino Acid
20 different kinds incorporated into proteins, and it has to be incorporated into a protein to be considered an amino acid.
Secondary Structure (Protein)
Results from interactions in nearby amino acids.
A-helices and B pleated sheets
Tertiary Structure (Protein)
3-dimensional shape of a polypeptide, hydrophobic and hydrophilic interactions, H-bonding, Disulfide bridges.
Quaternary Structure (Protein)
Results from interactions of polypeptide subunits.
Special Amino Acids
Glycine, Proline, Cysteine
Glycine
Allows for rotation
Proline
Allows for rigidity
Cysteine
SH groups cause disulfide bonding, hold 3-dimensional shape
Peptide bond
Formed by dehydration synthesis, links carboxyl end to the amine end
Alpha Helix
Each carboyl group in the backbone forms an H-bond with an amine group four residues away.
Beta Pleated Sheet
Adjacent strands can run in the same direction or in opposite. Hydrogen bonds form between carbonyl groups in one polypeptide and amide groups in a different part of the polypeptide.
Aminoacyl tRNA synthetases
Charge tRNA with the correct amino acid
Ribosome structure
Large subunit and small subunit. Large subunit has the exit site, the peptidyl site, and the aminoacyl site.
Reading Frame
Determined by ribosomes, when mRNA is read in groups of three.
tRNA structure
DHU loop, anticodon loop, T(psi)C loop, amino acid attachment site
Components of Translation
Initiation, Elongation and Release factors. Aminoacyl tRNA synthetases, tRNA, Ribosome, mRNA
Marshall Nirenberg
Credited with coming up with the genetic code and explaining how it works in protein synthesis.
Wobble Effect
Third position of a codon can sometimes change out and the same amino acid will still exist and be placed in the correct spot
Translation Process
Initiation is at the 5’ cap and AUG is the start codon. Initiation factors recruit the small ribosomal subunit and tRNA(met) and scan the mRNA far AUG. Initiation factors are released and a tRNA complimentary to the next codon binds to the A-site. A reaction transfers the Met to the amino acid on the tRNA in the A-site forming a peptide bond. The now uncharged tRNA is moved into the E site and the tRNA(val) moves into the PP site, and a new tRNA binds to the A site. Bond connecting polypeptide to the tRNA breaks after stop codon causes termination. Release factor binds to the A site.
Initiation in Prokaryotes
Located at any Shine-Dalgarno sequence; therefore the mRNA produced is polycystronic- can code for multiple polypeptides. Prokaryotes can have multiple proteins being made at once.
Shine-Dalgarno Sequence
Occurs before the start codon, and signals for the initiation of translation.
Post-translational Modifications
Addition of glucose, phosphate lipids, carbs
Addition of an acetyl or methyl group
Cleave off a piece of the peptide.
Initiation
initiation factors recruit the small subunit of the ribosome along with a charged tRNA that codes for Methionine. The start codon is AUG
and the anticodon found on the tRNA is UAC. When the start codon is found the large subunit comes and the mRNA transcript is now ready to be read properly
now that we know the reading frame
Elongation
The tRNA for methionine moves from the A site to the P site, where
the amino acid forms a peptide bond with the incoming amino acid. Methionine tRNA moves down one more to the E site known as the Exit site where it leaves
Termination
When a stop codon is encountered, a protein release factor binds to
the A site, breaking the bond between the polypeptide chain and the tRNA of the last amino acid, creating a C terminus of the polypeptide chain
Proteins are listed from the ____ end to the ____ end
Amino, Carboxyl