Structure of Protein

Structural Organization of Proteins There are different protein structures, and these correspond directly to the kinds of functions that the proteins address. While many people feel that protein is all the same, this is not the truth. With a number of different kinds of proteins and a wide array of uses for them, it stands to reason that the structural organization of proteins will be different based on each one of those proteins and what type of function it has (Murray, et al., 2006).

However, all proteins are similar in that they fold in three dimensions. The structure of the proteins are organized in a hierarchy that begins with the primary structure and moves through to the quaternary structure. Motifs and domains are the higher-level structures (Murray, et al., 2006). The primary structure services the polypeptide chain, and is a sequence of various residues (Van Holde & Matthews, 1996).

That is generally where the similarities end, and the wide variety of formations in the structural organization of proteins comes from the number of different sequences that are available in the amino acid residues. Without those differences, all proteins would be much more similar to one another, but that could also restrict them too much and keep them from doing the jobs for which they are currently designed. All proteins are constructed out of amino acids. A dipeptide is when two amino acids link together.

Oligopeptide is the term used for three to nine amino acids linked to one another, and polypeptide is used to describe a blending of more than that. Proteins are polypeptides, and are sometimes groups of a number of polypeptides that link to one another (Tooze, 1999). That can result in very complex proteins, such as would be found in some foods and in various workings of the human body. Typical proteins have 135 to 165 amino acids contained within them (Tooze, 1999).

While there are only 20 common amino acids, there are many more that are not seen as commonly, but that still have to be collected and contained in order to ensure a particular protein (Murray, et al., 2006) develops properly and can function correctly. There is a structure to proteins, as well, so they can remain organized and do their jobs. The primary structure is most important, as it is what gets the protein started and makes up the most significant part of it.

Without a good primary structure, the protein will not be able to perform its duties. That can lead to breakdowns of bodily functions, and can cause serious harm. It is important to identify more than just the primary structure when it comes to proteins, however, because the primary structure is not enough to provide everything the protein needs when it comes to form and function (Van Holde & Matthews, 1996). Other structures are built around that primary structure, strengthening the protein and developing it.

The secondary structure is formed through backbone atoms and the hydrogen bonds that can be made between them. It is a regularly occurring structure within the protein, and important for the proper creation and development of proteins (Murray, et al., 2006). The backbone atoms are considered to be the building blocks for this type of structure, which bonds together these atoms through the merging and mingling of hydrogen (Van Holde & Matthews, 1996).

Loops, coils, or turns do occur, and when they do they are not seen as being a stable part of a secondary structure (Van Holde & Matthews, 1996). That does not mean they are not supposed to occur, but only that they are insufficient to provide the needed stability of a protein's secondary structure. Instead, there are only two types of secondary structures that are designed to be stable. These are the alpha helices and beta sheets (Tooze, 1999).

Without the stability of these secondary structures, the proteins can come apart or completely fail to form (Tooze, 1999). This breaks them down, making them less usable and less valuable. Within the human body, that could become a serious health issue. These alpha helices and beta sheets can and should be seen at the core of the protein, where they provide the highest level of secondary stability and also have the most protection from damage (Murray, et al., 2006).

By being at the core, they are both protectors and protected, making them a vital component of proteins and increasing the likelihood that the protein will form correctly and function the way it is supposed to. The coils, turns, and loops are more generally seen around the edges of the protein, and not toward the core, or middle. These provide the protein with much of what it needs in order to function correctly, but stability is not one of the valuable assets of these loops, turns, and coils (Tooze, 1999).

After the secondary structures come the tertiary structures, which are third in line to provide structure and stability to a protein (Tooze, 1999). These describe how alpha helices, beta sheets, and random coils all pack together and interact with one.