Proteins are a necessary part of the human diet. When proteins are digested they are broken down into their building blocks – amino acids. The body then reassembles these amino acids to produce the proteins required by the organism to live. Proteins play essential roles in all living things, including humans. These roles can be included into two major types – structural and metabolic. Structural proteins maintain the shape and form of the both the individual cells of the body and the whole organism and are essentially responsible for locomotion. As an example, collagen is an essential ingredient of the connective tissue and is the most abundant protein found in the body. In addition, the movement of muscle is due to a fundamental property intrinsic to the structure of muscle proteins – actin and myosin.
A specialized class of proteins called enzymes is responsible for all the metabolic reactions that make life possible. There are thousands of different types of enzymes; each responsible for a particular chemical reaction. The scientific discipline that studies these reactions is referred to as Biochemistry. An example of a protein that plays a critical role in respiration is hemoglobin. The structure of this protein is exquisitely designed to react with molecular oxygen that is delivered to the lungs from the air. This protein, like all proteins, is synthesized from the blueprints that are embedded in the gene responsible for its structure. There is an axiom in biology that states that one gene has the information for the structure of one protein – this axiom basically still holds true. Because the structural information for a protein lies in the gene that is responsible for it, a change in a gene – a mutation – can adversely impact protein structure. Such a change would, therefore, be hereditary. Sickle Cell Anemia is a disease in which a mutation in the gene that contains the information for the structure of hemoglobin results in a change in the protein's structure that adversely impacts it function.
The techniques devised by molecular biologists and biochemists over the years have helped elucidate the detailed relationships between the structure of proteins and their specific functions. For example, as a result of these efforts, a relationship has been clearly demonstrated between the amino acid glutamine and protein structure. Studies have shown that when there are sufficient repeats of this amino acid – a number of glutamines linked side by side in the protein chain - they may cause a significant change in the overall shape of the protein resulting in protein aggregation. Protein aggregation can adversely affect protein or enzymatic function. The evidence indicates that when these glutamine repeats become extensive in the protein huntingtin and other proteins found in neurological tissues, the result can be neurodegenerative disease. The gene that contains the information for the structure of huntingtin is called the Huntington gene (HTT) and is strongly implicated in Huntington disease – a devastating neurological illness.
In conclusion, the examples cited above clearly demonstrate the essential role that proteins play in the human body and the implications for human health when protein structure has been changed due to a genetic aberration. Linus Pauling, the famous Nobel Prize – winning chemist, described diseases like Sickle Cell Anemia and Huntington disease as "molecular diseases" for the reason that the underlying cause can be traced to an adverse change on the molecular level.