In your own word Describe the following items in 26 sentence

In your own word, Describe the following items in 2-6 sentences.

1) How many disulfide bonds are in the insulin protein? Look up and define (in your own words) a disulfide bond.

2) Since insulin is a secreted protein, where is it translated in the cell? Why is this translation-location important for its secretion?

3) What do glucagon regulate in responding cells? What does insulin regulate in responding cells?

Solution

1- Insulin protein contains two inter-chain disulfide bonds. they are in between the A and B chains (A7-B7 and A20-B19). then there is one intra-chain linkage in the A chain itself. so altogether three disulphide bonds. A disulfide bond, is a covalent bond obtained from two thiol groups. It also called an S-S bond, or disulfide bridge,

2 - The insulin mRNA is translated as a single chain precursor called preproinsulin. While inserting into endoplasmic reticulum, the signal peptide is removed and proinsulin is generated.Proinsulin has three domains which are as follows - an amino-terminal B chain, a carboxy-terminal A chain and a connecting peptide known as the C peptide. Inside endoplasmic reticulum, proinsulin is exposed to several specific endopeptidases that excise the C peptide. this generates mature insulin. Insulin is then packaged in the Golgi into secretory granules. These granules then accumulate in the cytoplasm. All this occur inside beta cells.