CHED 1304

Insulin is one of the shortest known proteins1. It is made up of fifty one amino acid residues and has a molecular mass of 5733 Daltons; such short proteins are usually referred to as polypeptides 1. This polypeptide is manufactured in and released by pancreatic cells called islets of Langerhans in response to high blood glucose. Insulin directly binds to the muscles, fat and primarily liver via tyrosine kinase intracellular receptors2. In addition insulin indirectly targets the liver, as shown by Pocai et al, by affecting the hypothalamus through a KATP pathway to exert a nervous system method of control on the liver 3. These KATP channels release potassium in response to a drop in ATP and monitor blood metabolites and glucose. The insulin crystals in this experiment were grown by two methods, the hanging drop vapor diffusion method and the micro batch method. X-rays from the R-axis-IV diffractometer were focused at the crystal from different angles to produce diffraction patterns which were collected by the Crystal Clear 1-3.6 program, and stored on a computer hard drive. Using the HKL 2000 program, these diffraction patterns were then scaled and indexed to compare the patterns with known protein patterns, thereby determining their validity. The purpose of this experiment was to determine the structure of insulin. The Zn-Free bovine insulin was solved to reveal a tetragonal, face centered monomer belonging to the space group I213. With knowledge of a protein's structure, binding sites could be determined which could lead to the production better drugs, for example creating insulin-analog drugs that mimic insulin binding for insulin dependent diabetes patients 4.