Primary Structure

Of course, the formation or the putting together of a protein does not stop at the dipeptide stage. Instead, these two amino acid residues are bonded to another amino acid, which in turn is bonded to another, which in turn is bonded to still more. In the process, quite an extensive arrangement of amino acid residues are built up to form a protein. This sequence of amino acid residues is generally represented using the abbreviations and is referred to as the primary structure of the protein.

Primary structure of protein shown in a tetrapeptide. [68031.jpg]

The primary structure or amino acid sequence is unique for each protein. The sequence in which the amino acids are attached to one another ultimately is dependent on the genetic code from DNA. This primary structure dictates the function of the protein indirectly through additional levels of structure.

Consider this analogy, the nature of a garden is dictated by the plants that are in it. It's function, whether it is to provide shade, protection, privacy, food or tranquility, is going to be dictated by the individual plants selected and the sequence and orientation of them with respect to one another. Similarly, what a protein will be able to do is going to be determined by what amino acids are joined to one another and the sequence in which they are joined. However, the primary structure alone cannot carry out the functions of protein. The amino acids bonded to one another in a line don't make a protein function anymore than plants lined up along a roadside or in a nursery make a garden.

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E-mail instructor: Sue Eggling

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