RCSB PDB Newsletter | Spring 2007

AN EXCERPT FROM THE DIARY OF INSU LIN

I have been diagnosed with diabetes Type I! The doctor told me I would have to inject insulin into my body because I don't have enough. He also gave me a pamphlet explaining insulin. This helped me realize how important (and overlooked) this small hormone is in our bodies.

Insulin, a hormone secreted by the pancreas, regulates glucose levels. It is comprised of two chains (α and β). When glucose levels rise, insulin is secreted from the pancreas, and binds to receptors on the cell membrane of glucose requiring cells. This causes transport proteins in the cell membrane to take up glucose from the bloodstream. Essentially, insulin initiates blood glucose homeostasis.

The three disulfide bonds in insulin are critical to its function - two of which are between the two chains, while one is within the α chain. They connect the two chains of amino acids that make the insulin and help determine the tertiary and quaternary structure of insulin. If the chains did not fold into their natural positions, the hormone would not function properly, since the insulin molecule would not have the structure required to bind to receptors. Therefore, insulin would not be able to function.

The sequence of amino acids is the primary structure of the protein. According to the principles of protein folding, hydrophilic (polar) amino acids are positioned on the exterior of the protein, while hydrophobic (non-polar) amino acids are on the interior. If the primary structure was to be altered by even one amino acid in the residues that bind to the insulin receptor, insulin wouldn't fold into exactly the right shape. This would inhibit the insulin's ability to bind to cell receptors.

The structure of insulin directly impacts the hormone function. If there were to be any critical change in primary structure or disulfide bond formation, the folding pattern of insulin could be altered. It would not bind to cell receptors and thus not help manage cell metabolism.

I built an insulin model to better understand insulin and the nonpolar amino acids (white tape) are in the center, and polar amino acids (blue tape) surround them. As represented in my model, acidic and basic amino acids remain close to neutralize each other. This is shown in the central helix of the beta chain.

This excerpt is part of the abstract submitted by West Windsor- Plainsboro's team - Aleesha Shaik, Linda Maa, Ilya Podkopaev - at the regional competition. It has been edited slightly.

Science Olympiad tournaments, which take place across the country, consist of a series of individual and team events that students prepare for during the year. During this competition, teams demonstrate their diverse skills and knowledge in many different events. In Forensics, teams identify polymers, solids, and fibers at a crime scene, while in Write It, Do It, students compose a description of a structure that will be the only guide used by their other team members to recreate that structure (sight unseen) with raw materials.

High school teams at the New Jersey Science Olympiad (NJSO) demonstrated their understanding of structure and function in the 2007 Protein Modeling trial events that were sponsored by the RCSB PDB. In this event, students identify key elements of a structure and demonstrate their knowledge of the protein by creating a three-dimensional model using Mini-Toobers, computer visualization tools, and RCSB PDB resources. The model is accompanied by a brief abstract that highlights the features shown in their model and discusses what the protein does. At the competition, teams also answer multiple choice and short answer-questions focusing on its structure and function.

As one team described, the students enjoyed "replicating protein molecules that are found in the body into real-life toober models". The entries are judged by the RCSB PDB annotators using a model built directly from the structure's PDB file and a predetermined rubric that awards points for accurate depictions of the protein's features. For example, judges look to see if the N- and C- terminus are labeled properly and carefully consider the helices of the model. They also consider if the main functional and structural features of the protein are described in the written abstract. The written exam asks questions based upon the entry's Structure Summary page, the Molecule of the Month entry, and beyond. In 2007, teams built an insulin structure (PDB ID 4hiu) for the regional competitions held in January, and a section of a major histocompatibility complex (MHC) structure (PDB ID 1hsa) for the state competition in March. The hand-built models were really impressive, and the written abstracts and exams exhibited that many teams were quite scientifically literate.

At the Central New Jersey regional, East Brunswick High School (First Place and the 2006 State Champions in this event), West Windsor-Plainsboro South High School (Second), and West Windsor-Plainsboro North High School (Third) created very strong models.

At the Northern New Jersey regional, Bergen County Academy (First Place), Westfield High School (Second), and New Providence High School (Third) exhibited very strong skills.

At the state finals, students from all over the garden state competed. The highest ranked teams were Princeton High School (First Place), Montgomery High School (Second), and The Lawrenceville School (Third).

The Science Olympiad is an international nonprofit organization devoted to improving the quality of science education, increasing student interest in science and providing recognition for outstanding achievement in science education by both students and teachers. The 2007 NJSO (www.njscienceolympiad.org) was presented by the New Jersey Science Teachers Association and the New Jersey Science Education Leadership Association. Special thanks to the Center for BioMolecular Modeling at the Milwaukee School of Engineering (www.rpc.msoe.edu/cbm) for the design of this event. Kits similar to those provided for this event may be purchased from www.3dmoleculardesigns.com. Questions about the NJSO Protein Modeling trial event should be sent to buildmodels@deposit.rcsb.org.

A website with information and resources for participating in the protein modeling event can be found at education.pdb.org/olympiad.

Education Corner: 2007 New Jersey Science Olympiad