Lecture 8: Translation and Protein Synthesis

These flashcards cover the molecular biology of translation, including mRNA export, ribosomal structure, the genetic code, and the mechanics of protein synthesis as outlined in Human Molecular Genetics Lecture 8.

Central Dogma of Gene Expression

The process through which the information contained in DNA is expressed via the production of mRNA (transcription) and the synthesis of proteins (translation).

Alpha-keratin

A protein that forms hair and fingernails and is the major component of feathers, wool, claws, scales, horns, and hooves.

Actin and Myosin

Muscle proteins that enable all muscular movement, from blinking to breathing.

Hemoglobin

A protein that carries oxygen in the blood to every part of the body.

Ion channel proteins

Proteins that control brain signaling by allowing small molecules into and out of nerve cells.

Antibodies

Proteins that help defend the body against foreign invaders, such as bacteria and viruses.

Translation

The process of forming a polypeptide using mRNA as a template for amino acid sequence, occurring after mRNA enters the cytoplasm.

Nuclear Pore Complex (NPC)

A cylindrical structure with 8-fold symmetry that provides a channel for transport between the nucleus and the cytoplasm; small molecules less than $9\,nm$ pass freely, while those between $9\,nm$ and $28\,nm$ must be transported.

HnRNP A1 and HnRNP K

Common export proteins involved in the translocation of mRNA through the nuclear pore.

5’ CAP Binding Complex

A complex where the 5’ CAP of mRNA acts as an export signal and plays a role in directional translocation with the 5’ end in the lead.

CRM1

An export receptor that binds the export signal and carries mRNA to the other side of the nuclear pore.

RanGTP

A protein required for the export protein to bind the export signal in Ran-dependent transport; the complex dissociates when it is hydrolyzed to RanGDP.

TAP/NXT1

A heterodimer that acts as an mRNA exporter in Ran-independent nuclear transport pathways.

Karyopherins

A group of proteins involved in transporting molecules between the cytoplasm and the nucleus of a eukaryotic cell.

Ribosome Large Subunit (60S)

A ribosomal component containing $5S$ rRNA ($4,718\,bp$), $5.8S$ rRNA ($160\,bp$), $28S$ rRNA ($120\,bp$), and $49$ proteins.

Ribosome Small Subunit (40S)

A ribosomal component containing $18S$ rRNA ($1875\,bp$) and $33$ proteins.

A site

A binding site on the ribosome that holds tRNA carrying the next amino acid to be added to the polypeptide chain.

P site

A binding site on the ribosome that holds tRNA carrying the growing polypeptide chain.

E site

The site on the ribosome where discharged tRNAs leave.

Codon

A triplet of nucleotide bases that serves as the smallest unit coding for a single amino acid.

AUG

The codon that codes for the amino acid methionine (Met) and serves as the start codon for translation.

Stop Codons

The three codons that end translation: UAA, UGA, and UAG.

Transfer RNA (tRNA)

A molecule $74-95\,bp$ in length with an anticodon arm and an acceptor arm, responsible for transferring amino acids from the cytoplasm to the ribosome.

Shine-Dalgarno sequence

A $9\,bp$ long mRNA binding site recognized by the $16S$ rRNA on the ribosome to facilitate translation initiation.

Peptide Bond

An amide bond that connects the amino group of one residue with the carboxyl group of a second residue, forming the protein backbone.

Release Factors

Proteins that aid the ribosome in recognizing a chain termination codon (UAG) and initiate the release of the completed polypeptide.

Polysome

A structure consisting of a number of ribosomes each translating the same mRNA sequentially.

Alpha-amino acid (a-amino acid)

A standard amino acid where both the amino group ($-NH_2$) and carboxylic acid group ($-COOH$) attach to a tetrahedral $\alpha \text{-carbon}$.

Frameshift

A change in the reading of an mRNA message downstream caused by the insertion or deletion of any number of nucleotides that is not a multiple of three.

Wobble hypothesis

The theory that the first two bases in a codon create coding specificity, while the third position can be mismatched, allowing fewer than $61$ tRNAs to handle all coding codons.

Aminoacyl-tRNA synthetase

Enzymes that charge each tRNA with the proper amino acid by attaching the carboxyl group of the amino acid to the $3'\text{-OH}$ group of the $3'$ terminal adenine nucleotide.