PRIMARY PROTEIN STRUCTURE CODE

Hence, provided that cloning, expression and purification were successful, enough quantities of pure proteins could be employed in biochemical experiments or used to prepare solutions for NMR spectroscopy or to grow crystals for structure determination by X-ray crystallography. A protein of interest had its coding sequence identified and cloned in a proper expression vector. Proteins have traditionally being studied individually. Explosion of Biological Sequence and Structure Data This is other important fact on studying these molecules classical biological, physical, chemical, mathematical and informatics sciences have been working together in a new area known as bioinformatics to allow a new level of knowledge about life organization ( 13).Ģ. We must understand how these molecules fold, how they assemble into complexes, how they function if we wish to answer questions such as why we have cancer, why we grow old, why we get sick, how can we find cures for many diseases, why life as we know it has evolved in this way and on this planet and not anywhere else, at least for the moment.Īll proteins functions are dependent on their structure, which, in turn, depends on physical and chemical parameters. That is the reason why studying proteins, their composition, structure, dynamics and function, is so important. A remarkable fact is that all tasks they can perform are based on a common principle, the twenty amino acids that can form a protein. These are only some examples of protein function. All processes taking place in a living organism have proteins acting somewhere, in a precise way, developed under the pressures of natural selection. Biochemical reactions of cell breathing, oxygen and carbonic gas transport, food absorption, energy usage, energy storage, heat or cold physiological reactions, or any life process one can figure out, is basically carried out by a protein, or a protein complex. Such recognition processes occurs via protein-protein interactions on the surface of the immune system's cells, where binding affinity can determine if an immune response will or will not be initiated, and also where non-appropriated protein interactions or recognition can cause auto-immune diseases ( 11, 12). The immune system, responsible for our body's defense, is based on structure recognition, on differentiation of self from non-self this can only be possible through specialized cells that can bind and identify what is foreign to the body. Not only the DNA molecule cannot replicate itself without protein machinery such as the transcription complex, or transcription bubble ( 9) but also the mitosis and meiosis events of cell duplication and gamete production cannot go on without proteins performing crossing-over events and chromosome segregation ( 10).

Structural proteins, for example, are responsible for the cell integrity and cell overall shape ( 5), their functions varies from composing the cytoskeleton ( 6) to assembling transmembrane ion channels ( 7, 8), a structure essential for cell osmolarity and even for synaptic information flux. Molecular Function is the category that describes the tasks performed by individual proteins and can be broadly divided into twelve subcategories namely cellular processes, metabolism, DNA replication/modification, transcription/translation, intracellular signaling, cell-cell communication, protein folding/degradation, transport, multifunctional proteins, cytoskeletal/structural, defense and immunity, and miscellaneous functions. The Gene Ontology Project ( 4) uses three categories to describe a gene product or protein. It is worth mentioning that efforts are underway to make proteins of unnatural amino acids as well ( 2, 3). These proteins may have a constitutive or transient cell expression in regard to its functions.

PRIMARY PROTEIN STRUCTURE CODE

These twenty amino acids can be grouped together forming polypeptide chains, or proteins, in different ways determined by the genetic code and limited by stereochemical properties. There are twenty natural amino acids, whose frequency is higher than other special ones with particular functions.

Although the information necessary for life to go on is encoded by the DNA molecule, the dynamic process of life maintenance, replication, defense and reproduction are carried out by proteins. They are the building blocks of all cells in our bodies and in all living creatures of all kingdoms.

Proteins are molecular devices, in the nanometer scale, where biological function is exerted ( 1). In the drama of life on a molecular scale, proteins are where the action is ( 1).

Primary protein structure