Quaternary Tertiary Structures of Multiple Proteins Composed
The tertiary structure of a protein is the overall fold of the polypeptide chain so that it forms a certain 3-dimensional structure. For example, the tertiary structure of an enzyme is often dense, globular in shape. A tertiary structure is a combination of a variety of secondary structures. Tertiary structures are usually lumps. Some protein molecules can interact physically without covalent bonds to form stable oligomers (for example dimers, trimers, or quarters) and form quaternary structures.
These folds are controlled by hydrophobic interactions, but the structure can be stable only if the parts of the protein are locked into place by specific tertiary interactions, such as salt bridges, hydrogen bonds, and tight side chain packaging and disulfide bonds.
The tertiary structure of a protein is an overlapping layer over a secondary structural pattern consisting of irregular twists of bonds between side chains (R groups) of various amino acids (Figure 9). This structure is a three dimensional conformation which refers to the spatial relationship between secondary structures. This structure is stabilized by four types of bonds, namely hydrogen bonds, ionic bonds, covalent bonds, and hydrophobic bonds. In this structure, hydrophobic bonds are very important for proteins. Amino acids that have hydrophobic properties will bind to the inside of globular proteins that are not bound to water, while amino acids that are hodrophilic in general will be on the outside surface that binds to the surrounding water (Murray et al, 2009; Lehninger et al., 2004).
Tertiary structure
Quartener structure
Some proteins are composed of more than one polypeptide chain. Quartener structures describe different subunits that are used together to form protein structures.
The quaternary structure is a picture of the arrangement of sub-units or protein promoters in space. This structure has two or more of the protein sub-units with tertiary structures that will form functional protein complexes. the bonds that play a role in this structure are noncovalent bonds, namely electrostatic, hydrogen and hydrophobic interactions. Proteins with quaternary structures are often referred to as multimeric proteins. If a protein composed of two subunits is called a dimeric protein and if it is made up of four subunits it is called a tetrameric protein (Figure 10) (Lodish et al., 2003; Murray et al, 2009).
Quartener structure
Judging from its structure, proteins can be divided into 2 groups, namely:
A simple protein which is a protein consisting only of amino acid molecules. Included in the group for example:
Protamin
This protein is alkaline and does not experience coagulation on heating.
Albumin
Protein is soluble in water and aqueous salt solution, the BM is relatively low. Albumin is found in egg white (egg albumin), milk (lactalbumin), blood (blood albumin) and vegetables.
Globulin
Soluble in neutral salt solution, but not soluble in water. Coagulated by heat and will settle to a high concentration of salting solution (salting out) in the body there are many antibodies and fibrinogen. In milk there is in the form of lactoglobulin, in eggs ovoglobulin, in the meat of myosin and acitin and in soybeans called glycillin or generally in legumes called legumin.
Glutelin
Soluble in dilute acids and bases, but not soluble in neutral solvents. Example: gluten in wheat and oryzenin in rice.
Prolanin
Soluble in ethanol 50-90% and insoluble in water. This protein contains a lot of proline and glutamic acid, and there are many in the serelia. For example: zein in corn, gliadin in wheat, and cordurine in barley.
Scleroprotein
Insoluble in water and neutral solvent and resistant to enzymatic hydrolysis. This protein functions as a protective structure in humans and animals. Examples of collagen, elastin, and keratin.
Histones
Is a basic protein, because it contains lysine and arginine. Is soluble in water and will be clotted by ammonia.
Globulin
Almost the same as histones. Globulin is rich in arginine, tryptophan, histidine but does not contain isoleucines found in the blood (hemoglobin).
Protein
A very simple protein, BM is relatively low (4000-8000), rich in arginine, soluble in water and coagulated by heat and is basic.