The protein, Transgultaminase 2 is a key component in the process of gum disease, researchers have discovered. Periodontal, or gum, disease is one of the most common infectious diseases. In its more severe forms, such as periodontitis, it causes loss of the bone that supports the teeth. Approximately 65 million adults in the United States are affected by some form of the disease. PG is the major causative agent of periodontitis, and it may also be involved in the development of systemic diseases such as atherosclerosis and rheumatoid arthritis.