Researchers can also gain additional information by changing a protein’s amino acid sequence and seeing how each change affects the protein’s activity. Researchers have developed techniques to visualize the 3D shape of a protein, including X-ray crystallography, nuclear magnetic resonance spectroscopy (NMR), and cryo-electron microscopy (cryo-EM). In a process called translation, the ribosome reads the mRNA and converts it into a chain of amino acids, which then folds into a protein. First, RNA polymerase copies these instructions in the form of messenger RNA (mRNA), which passes through a cellular “machine” called a ribosome. Proteins are built based on instructions stored in DNA. Credit: Center for Eukaryotic Structural Genomics, PSI. This model illustrates human aspartoacylase, an important enzyme involved in brain metabolism. Some proteins are only a few dozen amino acids long, while others consist of thousands of amino acids. A protein’s shape and orientation enable it to do its job. For example, hydrophobic (water-fearing) amino acids will arrange in the center of a protein away from water molecules, while hydrophilic (water-loving) amino acids will arrange on the outside of the protein in contact with water molecules. An amino acid’s side chain dictates its behavior. There are 20 amino acids commonly found in nature, each containing the same backbone structure plus a unique attachment called a side chain. Proteins are chains of amino acids joined by chemical bonds like a string of beads. For example, cytokines are the protein messengers of the immune system and can increase or decrease the intensity of an immune response. Some proteins act as chemical messengers between cells. Those with lactose intolerance don’t produce enough lactase to digest dairy. For example, lactase is an enzyme that breaks down lactose, a sugar found in dairy products. Many proteins are biological catalysts called enzymes that speed up the rate of chemical reactions by reducing the amount of energy needed for the reactions to proceed. Proteins such as actin make up the three-dimensional cytoskeleton that gives cells structure and determines their shapes. Credit: Xiaowei Zhuang, HHMI, Harvard University, and Nature Publishing Group. Continued abuse of our services will cause your IP address to be blocked indefinitely.Actin proteins in a cell’s cytoskeleton. Please fill out the CAPTCHA below and then click the button to indicate that you agree to these terms. If you wish to be unblocked, you must agree that you will take immediate steps to rectify this issue. If you do not understand what is causing this behavior, please contact us here. If you promise to stop (by clicking the Agree button below), we'll unblock your connection for now, but we will immediately re-block it if we detect additional bad behavior.
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