Protein Synthesis

protein synthesis occurs in

the cytosol

rate limiting step of translation

first amino acid being placed

redundancy/degeneracy

usually manifests in 3rd nucleotide (wobble position)

Hsp70

chaperone proteins that bind to the polypeptide and protect against misfolding, can be facultative or constitutive

Hsp60

forms a cylindrical barrel to achieve proper folding and 3d conformation of the protein

polysome

one mRNa has many ribosomes attached, each making their own protein

signaling sequence in polypeptide

will pause translation and move the protein ribosome complex to the cisternae of the ER

rough ER

synthesizes ribosomes

smooth er

• abundant in ovaries, liver, and testes

• makes lipids

• functions in detox reactions

steps of traslation involving ER

• protein begins synthesis on the free ribosome

• signal sequence on N terminus is reached

• SRP binds to signal sequence

• attahces to the ER lumen

• translation continues

• signal peptidase cleaves polypeptide

• polypeptide may be packaged into vesicles and secreted

binding proteins

chaperone proteins that may attach to the polypeptide inside the lumen of the ER to prevent misfolding

vesicles leaving ER

• vesicles move proteins between cisternae

• moves to cis face of golgi

• delievered out of trans face to fuse with PM

stop codons in ER

allow transmembrane proteins to form, termini can go either way

modifications that occur in the lumen of the ER

• N glycosylation

• disulfide bonds

• GPI lipid link

N glycosylation

• addition of sugar to the N of asparagine

• protective against proteases

• functions in recognition in the ECF

GPI linkages

• protein has signal and stop sequences for TM protein

• start transfer peptide cleaved off

• protein is cleave and transferred to GPI lipid anchor

Hematouria

red blood cells get destroyed by immune system cells that mistakenly target their lack of lipid link

disulfide bond formation

• occurs in oxidative ER lumen

• get broken and reformed by protein disulfide isomerase