Biochem - Protein Synthesis

Front 1

start codon

Back 1

aug

Front 2

stop codons

Back 2

uag, uaa, uga

Front 3

explain coding vs noncoding strand

Back 3

coding strand looks like mRNA, non coding is the template. The noncoding strand may be known as the template or antisense strand

Front 4

silent mutations

Back 4

altered codon codes for same AA

Front 5

nonsense mutations

Back 5

termination of strand (stop the nonsense)

Front 6

what mutations cause osteogenesis imperfecta

Back 6

mutations to collaten type 1 gene COL1A1 or COL1A2

Front 7

point mutation

Back 7

alterd codon codes for a different amino acid

Front 8

How do most mutations in OI work

Back 8

mutation of glycine to a more bulky residue causing chain kinking and a weakening of the collagen fibrils

Front 9

therapy for OI

Back 9

antisense therapy to reduce the number of expression of mutant genes to convert severe OI to mild OI

Front 10

What is the genetics term for a disorder resulting from multiple possible mutations in a gene?

Back 10

Allele heterogeneity

Front 11

Explain the genetic mutations associate with cystic fibrosis

Back 11

over 1000 different mutations can occur in the CFTR gene to cause cystic fibrosis. The cell recognizes it as misfolded and degrades it.

Front 12

Explain the genetic mutations associated with sickle cell anemia

Back 12

a single point mutation in the hemoglobin A chain causes a sickling of the RBC's. This is where a Glu is converted to a Val. It is a transversion

Front 13

the two mechanisms of t-RNA loading and codon-anticodon complementarity which ensure the accuracy of translation

Back 13

Recognition of an mRNA codon is accomplished by the tRNA anticodon. The anticodon binds to the codon following the rules of complementarity and antiparallel binding. (When writing the sequences of both codons and anticodons, the nucleotide sequence must ALWAYS be listed in the 5’ to 3’ order.)

Front 14

Overall steps of protein synthesis

Back 14

1. Activation of amino acids, 2. begin protein synthesis 3. chain elongation 4. discontinue synthesis

Front 15

what initiation factors are necessary for the pre-initiation complex

Back 15

elF2 and elF4/GTP

Front 16

where and with what does mRNA bind to the 40S ribosomal subunit

Back 16

tRNAiMet in the P-site

Front 17

What is present at the initaition complex

Back 17

40S and 60S subunits, with the anti-codon UAC and starting codon AUG (which codes for Met). elF2 w/ GDP+Pi and elF48 is hydrolyzed.

Front 18

What does EPA stand for

Back 18

exit E, P , A sites. The P site contain the peptidyl-tRNA (filled w/ Met-tRNA iMEt) and A has aminacyl-tRNA.

Front 19

what happens during chain elongation

Back 19

elongation factors attach to the tRNA’s, in particular EF1 which hydrolyzes GTP to add to the growing polypeptide chain.

Front 20

What causes the chain to move over one spot

Back 20

EF2 (GTP hydroylzation) is involved in moving the tRNA to one site over, for example, moving it to the P to E site, and from the A to P sites.

Front 21

What happens during termination

Back 21

a stop codon enters the A site, and this signals the growing polypeptide to be released with the help of RF1 and RF2 release factors which uses GTP as well.

Front 22

  Where does the catalytic activity for peptide bond formation reside?

Back 22

The formation of the peptide bonds, peptidyltarnsferase, catalyzed by an activity intrinsic to the 23S rRNA found in the 50S ribosomal subunit.

Front 23

What would happen if drugs inhibiting translation targeted initiation inhibitors

Back 23

Inhibit association between mRNA and the prokaryotic 30S ribosome , freeze the prokaryotic initiation complex, inhibit prok peptide chain initiation which also induces mRNA misreading, cleave eukaryotic rRNA large subunit.

Front 24

What would happen if drugs inhibiting translation targeted elongation inhibitors

Back 24

Inhibit prokaryotic aminoacyl tRNA binding to the ribosome small subunit Inhibit prokaryotic peptidyl transferase, peptidyl transferase, Inhibit prokaryotic translocation through the ribosome large subunit, Interfere with peptide transfer resulting in premature termination in both prokaryotes and eukaryotes, v. Interfere with peptide transfer resulting in premature termination in both prokaryotes and eukaryotes , vi. Inhibits mammalian EF-2, inhibits translocation

Front 25

Explain posttranslational phosphorylation

Back 25

Phosphorylation occurs on the hydroxyl group of serine, threonine, or, less frequently, tyrosine residues in a protein. This phosphorylation is catalyzed by one of a family of protein kinases and may be reversed by the action of cellular proteinphosphatases. The phosphorylation may increase or decreasethe functional activity of the protein.

Front 26

Explain posttranslational hydroxylation

Back 26

Proline and lysine residues of the α-chains of collagen are extensively hydroxylated in the endoplasmic reticulum.

Front 27

Explain posttranslational acetylation

Back 27

(N-terminus, lysine) histone H4

Front 28

Explain posttranslational glycosylation

Back 28

Many of the proteins that are destined to become part of a plasma membrane or lyosome or to be secreted from the cell have carbohydrate chains attached to serine or threonine hydroxyl (O-linked) groups or the amide nitrogen of asparagine (N-linked).

Front 29

how and where proteins to be secreted are manufactured and directed in the cell

Back 29

Proteins are synthesized on ribosomes in the cytosol and translocated into the ER as they are synthesized. Proteins are then transported from the ER to the Golgi apparatus with a side route leading to lysosomes (for incorrectly folded proteins). Transport may be via vesicles which bud out from the donor compartment and fuse with the target compartment; transmembrane, using membrane-bound protein translocators, or through pores (eg. into the nucleus). Glycosylation (Asn, N-linked; Ser/Thr, O-linked) of proteins occurs in the Golgi apparatus - other types of post-translational modification occur as well. Extracellular proteins can be targeted for secretion, to the cell membrane, or to one of the many internal organelles. Intracellular proteins can be targeted for the cytoplasm, to the nucleus or to special organelles such as the mitochondrion or the chloroplast.

Front 30

What do proteins intended for secretion have and how does this work

Back 30

an initial highly hydrophobic sequence is called the signal peptide. The signal peptide is recognized by and bound by a signal recognition particle (SRP). The SRP is a protein-RNA complex. The RNA component is essential for binding with the signal peptide. When the SRP binds this stops further protein synthesis. The SRP-complex next docks with a SRP-receptor, inserting the signal peptide into the translocon in the ER membrane. The signal peptide crosses the ER membrane through the translocon and extends into the lumen of the ER. Protein synthesis now resumes, and the (now no-longer-required) signal peptide is cleaved off (by a specific signal peptidase inside the lumen of the ER).

Front 31

Explain protein processing of insulin

Front 32

What does ubiquitination do

Back 32

Proteins that are defective or destined for rapid turnover are oftenmarked for destruction by ubiquination – the attachment of a small, highly conserved protein, called ubiquitin. Proteins marked in this way are rapidly degraded by a cellular component known as the "proteasome", which is a complex, ATP-dependent, proteolytic system located in the cytosol.

Front 33

What is the action of chaperone proteins

Back 33

bind to hydorphobic surfaces to prevent interation, bind permanantely when misfolded, transport proteins into organelles or into cytoplasm for degradation, stress survival

Front 34

What class of diseases are thought to be the result of misfolded beta sheets

Back 34

amyolidoses