| Question |
Answer |
| describe the signal peptide |
20-30 AAs; usually at the amino terminus; mostly hydrophobic |
| Describe SRP |
signal recognition particle; complex proteins and 7S RNA; halts translation until it is bound to rER surface |
| Secreted proteins are often stabilized by what? |
disulfide bonds |
| Correct formation of disulfide bonds is helped by what enzyme with regards to protein folding in the ER? |
peptidyl disulfide isomerase |
| What is the default pathway for a protein without a signal? |
secretion |
| What is cotranslational import? |
uptake of protein into ER depends on continuing protein synthesis by the ribosome |
| What form of insulin does the insulin gene code for? |
preproinsulin |
| What is the single-chain form of insulin called without its signal peptide? |
proinsulin |
| What is KDEL? |
Lys-Asp-Glu-Leu; particular peptide sequence that causes proteins to be captured back from the Golgi |
| What is the targeting signal for sorting to the lysosome? |
mannose-6-phosphate |
| What is the mitochondrial import signal? |
N-terminal alpha helix with a series of basic AAs on one face |
| What genes do mitochondrial DNA code for? |
NADH dehydrogenase, cyto b, cyto oxidase, F1 ATPase |
| Is uptake into the mitochondrial membrane considered to be pre or post translational? |
posttranslational |
| What is the nuclear localization signal? |
5-6 AAs; basic and proline |
| Describe uptake of the protein into the nucleus. pre or post translational? |
post-translational |
| What is a common post-translational modification to the N-terminus? |
removal of methionine and acetylation |
| What are the two types of post-translational glycosylation? |
O-linked and N-linked |
| Describe O-linked post-translational glycosylation |
covalently bonded to Ser or Thr; one sugar at a time by glycosyltransferases |
| Describe N-linked post-translational glycosylation |
linked to Asn; must occur in Asn-Xxx-Ser/Thr sequence; |
| What is the general peptide sequence for collagen? |
Gly-X-Y; X= Pro; Y= 4-OHPro |
| Describe the collagen gene. |
50exons; 54bp's and 6GlyXY per base pair |
| What direction does the collagen triple helix form? |
C to N-terminus |
| What intracellular post-translational modifications occur in the formation of collagen? |
hydroxylations, glycosylations, protofibril formation |
| What enzyme helps for lysine aldehyde cross links? |
lysyl oxidase |
| What is the difference between collagen and procollagen? |
procollagen still has C and N-propeptides |
| Describe osteogenesis imperfecta. |
genetic disorder; characterized by easily breaking bones of varying degree; mutation in type I collagen genes |
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