In the review, the nature of protein multifunctionality is analyzed. In the first part of the review the principles of structural/functional organization of protein are discussed. In the second part, the main mechanisms involved in development of multiple functions on a single gene product(s) are analyzed. The last part represents a number of examples showing that multifunctionality is a basic feature of biologically active proteins.
The cell fulfills two main functions: storage of genetic information and transfer it to the next cell generation; synthesis of diferent molecules, protein molecules in particular, for fulfillment of numerous cell processes.
The compactness (maximum information packed in minimum DNA space) is one of the main principles of genetic information storage. The fulfillment of the first cell function is based on this principle. On the contrary, the abundance, variability and diversity of the protein molecules are necessary for realization of the second function. In contrast to DNA, proteins exhibit an apparently unlimited variety of structure. This is a necessary requirement of the vast array of different functions that they perform in the maintainance of life “in contrast to the relatively static archival function of DNA” (Lesk, 2001). In the protein world, not only “a bewildering variety of form is observed but even within a common structure, there is variation in the lengths and orientation of substructures. Such variation is both a reflection of the very long evolution of protein structures and also a consequence of the fact that proteins cannot be completely rigid bodies but must have flexibility to accommodate the structural changes that are almost always necessary for them to perform their functions” (Lesk, 2001).
All multiple variations in protein structures and functions are genetically determined by DNA sequence fixed in amino acid primary structure of a protein and can be achieved by different mechanisms operating at different levels.
At the level of genome, a single gene may undergo duplication followed by rearrangement and/or mutations thus leading to appearance of homologous proteins possessing partially similar and/or different functions.
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Protein multifunctionality: principles and mechanisms
