Molecular Insights into the Hormone Insulin
Insulin plays a major role in providing energy for cells to function, as it begins reactions that convert glucose into energy. It is a hormone that acts as a messenger to other cells to uptake glucose, allowing them to produce energy to continue functioning. Using Rasmol and Chem3D software, the molecular structure of insulin was examined to understand its binding with its receptor and to gain chemical insight into its activities related to the production of energy. The problem of insulin resistance is also briefly explored.
It is a well known fact that obesity is a growing problem in the United States; along with obesity comes a whole score of problems, mainly caused by malfunctioning insulin molecules within the body. Without insulin, the cells in our bodies slowly break down and stop functioning, since it is a hormone that has a range of functions. As proteins go, it is relatively small, made up of 460 atoms throughout 51 amino acids and its molecular weight is 5808 Daltons.5 Produced by the Islets of Langerhans in the pancreas, its primary purpose is to regulate carbohydrate metabolism. Along with that it increases fatty acid synthesis, potassium uptake, DNA replication and protein synthesis in cells, and forces the arterial wall muscle to relax.
Insulin is produced in the pancreas by beta cells, which then release it according to blood glucose levels. The protein assembly of insulin begins when an RNA transcript is translated into an inactive preproinsulin protein that has the amino acid sequence that allows it to pass through the endoplasmic reticulum membrane, after which it is changed into proinsulin. Active insulin is formed after specific peptidases “cleave” the proinsulin, and it is stored in granules that remain within the cytoplasm.4
As blood glucose concentrations rise, the pancreas is stimulated to release insulin into the bloodstream. Type 2 glucose transporters, GLUT2, regulate the entry of glucose into beta cells. The glucose is modified by a glucokinase enzyme and is metabolized to form ATP, energy molecules, through glycolysis. The increased ATP level in the cell causes potassium channels, which are “gated” by ATP, to close. This, in turn, causes the potassium ions and positive charge to build up and depolarize the cell. This activates the calcium channel, which is “voltage gated”, and calcium atoms flow into the cell, triggering the granules in the cytoplasm to release insulin. The insulin is released in two phases, once when glucose is absorbed, and once after being synthesized while stored molecules are released. 1
Once in the bloodstream, insulin molecules bind to transmembrane receptors, leading to an increase in the uptake of glucose from blood into muscle cells and adipose tissues as the glucose. The insulin receptor mediates activity by adding phosphate groups to specific tyrosines on different proteins within the cell, like the IRS-1 protein, which stands for...