Theme 2 - Mod 4 - The Complex Proteome

Human Proteome

Represents the full number of proteins that are expressed by all the hereditary information in our DNA

aka genome

Where is most glucose absorbed

Microvilli of small intestine

What do pancreatic beta cells do when glucose is absorbed

Detect an increase in blood glucose levels and adjusts the amount of synthesis and secretion of the insulin protein

What did Dorothy Hodgkin discover

Able to determine the structure of the functional insulin protein

How many amino acids is an insulin protein

110

What is the functional insulin protein made up of

Alpha chain with 21 amino acids

Beta chain with 30 amino acids

What is preproinsulin

110 amino acid precursor chain

What does the N-terminal in preproinsulin do

Interacts with SRP to facilitate translocation of preproinsulin into the lumen of the rough ER

How is proinsulin formed

Formed from cleavage of signal sequence in preproinsulin

How is insulin formed

Goes to golgi to undergo further processing to form the mature insulin dimer

Containing A and B chain and releasing C chain

Undergoes folding to form 3 disulfide bonds

Why are post-translational modifications important?

Increase the functional diversity of the proteome

Examples of post-translational modifications

Cleavage

Disulfur bonds

Covalent attachment of other molecules

Degradation of entire protein

How is a phosphorus added during phosphorylation

Phosphorus added through enzymes called kinases

What happens when insulin binds to the receptor kinases

Causes many cells in our body to transport glucose across the plasma membrane into the cytosol of the cell

What happens after glucose gets transported out the membrane

Each receptor attaches to a phosphate group and the phosphate group provides binding sites for intracellular signaling proteins

What does intracellular signals lead to

The activation of glucose transporter proteins at the cell surface and results in the absorption of glucose into the cell

Positive feed back loop in intracellular signaling

Initiation and maintenance of a signal to keep the signal and amplification on

Negative feedback loop in intracellular signaling

Leads to intracellular signal termination

Double negative feedback in intracellular signaling

Where an inhibitor signal can also be inhibited

Provides fine control in a cell in response to an extracellular signal

What does adipose tissue do

Takes glucose and fatty acids and stores it as triglycerides

What does the liver do to glucose

Takes up glucose in the blood and stores excess as glycogen

What occurs from eukaryotes being able to produce more than one mRNA transcript from a single gene

This result allows for a single gene to encode for more than one protein product, an thus contributes to proteomic complexity

Alternative splicing

Enables one pre-mRNA molecule to be spliced at different junctions to result in many different mature mRNA molecules that contain different combinations of exons

Why does alternative splicing occur

The spliceosome will sometimes recognize an exon as an intron in certain primary transcripts

What would happen if the insulin protein was not processed correctly following translation

There may not be the ability for this protein to bind to the insulin receptors on the targeted tissue