Any of a group of complex organic compounds or macromolecules containing carbon, hydrogen, oxygen, nitrogen, and usually sulfur, the characteristic element being nitrogen. Widely distributed in plants and animals, they are the fundamental constituents of the protoplasm of all living cells, and include many substances, such as enzymes, hormones, and antibodies, necessary for the proper functioning of an organism. Twenty different amino acids are commonly found in proteins (but see below), and each protein has a unique, genetically defined amino acid sequence that determines its specific shape and function. They serve, among other things, as enzymes, structural elements, hormones, and immunoglobulins, and are involved in oxygen transport, muscle contraction, electron transport, and other activities throughout the body, as well as in photosynthesis. They are essential for the growth and repair of tissue and can be obtained from foods such as meat, fish, eggs, milk, and legumes. The largest naturally protein is tintin (or connectin). It consists of no less 28,926 amino acids and is 189,819 letters long. Although it is not found in a dictionary, it is considered to be the longest word in the English, as well as the longest entry registered by the International Union of Pure and Applied Chemistry. In fact, takes 3.5 hours to read, a feat that has been completed and made public. The TTN gene is the source of instructions manufacturing the protein, and which becomes abundant in striated muscle forming the third filament of the sarcomere. Thus, in interaction with other muscle proteins, it plays a crucial in the contraction and stretching of striated muscle, as well as in cardiac muscle. Moreover, it provides flexibility, stability and structure to these muscle cells, and in the assembling new sarcomeres, as well constituting a structural protein for chromosomes. The development of the heart is also dependent on the protein. Mutations in the TTN gene give rise to more cases of dilated cardiomyopathy, a common cause of heart failure, than all known other mutations.
See Actomyosin, Amino acids, Aspartate acid (aspartic acid), Biochemistry, Bioinfomatics, Bone Morphogenetic Proteins (BMPs), Cell locomotion, Central dogma of molecular biology, Chordin, Chromatin, Chromosome, Collagen, Creatine, Cytokines, Cytoplasm, Elastin (gene), Enzyme, Fibroblasts, Glycoproteins, Growth hormone (or somatotropin), Homeodomain proteins and homeobox genes, Hormones, Immunoglobins, Interphase, Lamillipodia, Ligands, MECP2 gene, Methylation, Microtubules, Molecular biology, Mucins, Muscle fiber, Mutation (biology), Myoglobin, Myosin, Nissl substance, Noggin, Oxyhemoglobin, Peptides, Phosphorylation, Polymerization, Prion (proteinaceous infectious particle), Protein-folding problem, Protoplasm, Reelin, Sarcomere, Smooth (or involuntary) muscle, Striated (or striped or voluntary) muscle, Structural proteins