What is the Basic Structure of a Protein?

The basic structure of a protein can be differentiated into four, which are given below,

  • The primary structure, which is just a sequence of amino acids.
  • The secondary structure, which includes the alpha helix and beta pleated structure.
  • A tertiary structure is a three-dimensional folding structure.
  • Quaternary structure is a complicated one that shows more than one amino acid chain.

Among these, the tertiary structure of a protein is the one that gives them shape and it is very significant for its functionality. 

Tertiary Structure

The tertiary structure of a polypeptide network is its three-dimensional ultimate form after all the secondary structure components folded over each other. The intricate three-dimensional tertiary framework of a protein is created by the associations among polar, nonpolar, acidic as well as simple R group inside a polypeptide sequence where protein folding is performed in the body's aqueous system, non-polar amino acids are mostly located within the protein in hydrophobic R, while often on the external side are the hydrophilic R groups located. In the availability, of oxygen cysteine side chains create disulfide connections, the only covalent connection which forms while protein folding. All these associations define the ultimate 3D protein structure. If a protein starts losing its three-dimensional form, it won't work anymore.  

An image showing different structures of Protein


 Proteins are organic nitrogen molecules where a wide variety of amino acid sequences are combined into lengthy polypeptide sequences through peptide bonds. Peptide lin (-CONH)

vis developed by the elimination of a water group when the amino group (-NH2) of one amino acid combines with the carboxylic group (-COOH) of another amino acid. Also there are hundreds of amino acids, but only approximately 20 varieties of amino acids organize proteins in the plant in a single polypeptide chain known as essential amino acids. 

Interactions in Tertiary Structure

Several proteins transform itself into its tertiary arrangement. In order to fold the chemical characteristics of the different R-groups inside the protein chain are influenced. There are different interactions between the functional groups that stabilize the tertiary structure of protein. These can be identified as follows:  

Disulfide linkages  

These are the bonds that are formed between two cysteine molecules present near each other. The bond is formed between two sulfur atom S=S that are present among the monomers of cysteine.

Hydrophobic and Hydrophilic Interactions

The most significant element and organizing factor for forming the tertiary framework would be non-covalent connections. Few acids may have a hydrophobic effect and several might be hydrophilic. A globular protein in a water-based system can situate itself along its middle but also its hydrophilic components along its sides. Both the amino acids including hydrophilic lateral chains, including isoleucine, are present on the protein level, whereas hydrophobic lateral chains including Alanine are located at the protein core. The hydrophobic side groups in several globular proteins are phenylalanine, valine, or tryptophan, for instance, found within the protein framework.  In contrast, on the outer portion of the protein hydrophilic amino acids like glutamic acid, serine, and asparagine, while convenient for water activity, are usually present.  In the case of soluble protein, such groups sometimes form often load associations including salt bridges, taking a positive side chain (such as Arg) near to a negative one (such as Glu).  

Ionic linkages  

Amino acid chains present in the protein possess either a positive or a negative charge. When two differently charged groups come in proximity of each other they form an ionic bond. These linkages help in stabilizing a protein molecule.  

Hydrogen bonding  

Hydrogen bonding is the most commonly observed linkages that are formed between water molecules and the hydrophilic functional groups in the protein molecule. These linkages are also observed between polar molecules of the protein structure.  

An image showing different bonds in a tertiary protein

Classification of Tertiary Protein  

Tertiary proteins mainly falls into two categories namely, globular protein and fibrous protein.  

Globular protein  

This seems to be frameworks ball-like, whereby hydrophobic components are in the middle while hydrophilic therefore at boundaries that make it soluble in water. Normally these take part in different metabolism. With greater than one protein, there may be one domain where the protein has identical roles and even a multi-function protein where more than one framework each plays a particular role. The enzymes present in our cells are an example of globular proteins.

Fibrous protein  

They shape long filament which comprise predominantly repetitive, water-insoluble amino acid chains. They normally play supportive roles examples include collagen, fingernail and hair keratin.  

Denaturation of Tertiary Proteins  

The thermal activity will break the tertiary framework.  An increase in the kinetic intensity of a tertiary protein will cause it to rotate further therefore more probable to snap the attachments that sustain their form. This process is said to be denaturation when a protein molecule changes its structure. And if the protein cools, the initial structured form of protein would not develop.  

Proteins Involved in Folding  

Proteins may help several proteins fold. While the regular, functional protein arrangement is believed to be thermally highly reliable, it is not necessarily accomplished in a higher-yielding if the protein can fold itself. Most cells have a number of proteins known as chaperonins, which make it easier to fold recently processed and denatured proteins properly. In general, after the ultimate arrangement of the tertiary protein, disulfide associations develop. Since they are too solid, a passive tertiary configuration might be forced by the prematurely forming of a wrong hydrogen bond. If ribonuclease disulfides are able to develop while the protein is in denatured condition, for instance, just under 1% of the activity of the enzyme is restored and only a small percentage is accurate.  

If the protein is permitted to develop an appropriate tertiary structure until the development of disulfide, all enzyme behavior is effectively restored. The disulfide exchange enzyme is active on freshly created proteins, which mediates the disintegration of disulfides in a protein and rejoins them. In combination with the activity of chaperonins, the enzyme assists the protein in its ultimate, local condition, with the proper formation of the disulfide.  

Importance of Tertiary Protein Structure  

Tertiary structure of protein is important during enzyme reactions. It helps to create active sites in enzymes by changing the configuration and shape of protein. This is important for the active role of enzyme in catalysis favoring a particular reaction.  

Difference between Primary, Secondary, and Tertiary Protein Structure  

The main difference between the primary structure, secondary structure, and tertiary structure of protein lies in its structure. The primary structure of protein has linear arrangement whereas secondary structure protein structure can either be α- helix or β- sheet while the tertiary protein structure is globular in nature.  

Common Mistakes  

The common mistake can occur while understanding the structure of tertiary proteins where the hydrophobic amino acids are present inside the globular structures and the hydrophilic amino acids are present on the surface of the protein molecule enabling its interaction with surrounding environment.  

Practice Problem

If a given enzyme acts on the covalent bonds present in between two sulfur atoms that are not adjacent in the polypeptide chain, name the protein structure this enzyme is acting upon.  


Tertiary protein structure  

Context and Applications   

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for 

B.Sc. in Chemistry, Biotechnology, Biochemistry and Biology M.Sc. in Chemistry, Biotechnology, Biochemistry and Biology   

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