Question

Discuss the different levels of protein folding, giving example of particular folds. Discuss the difference between motifs and domains in folded proteins. Briefly discuss the difference between globular and fibrous protein structures.

Answer 1

The first level of structure of protein is its unfolded form which is commonly referred to as peptide chain. It is just the sequence of amino acids all of which are connected to each other by peptide Bond. Peptide bond is a covalent bond and the synthesis of proteins is a dehydration synthesis.

The second level of structure is the folding of peptide chain upon itself due to the hydrogen bonding between side Chains of amino acids. These are of two types, Alpha helix and beta pleated sheet. This is commonly called as motifs.

The third level of folding of protein is the tertiary structure of protein. It is the association of two or more motifs with each other. It is stabilized by the formation of many covalent and noncovalent Bond. It includes hydrogen bonding, ionic bonding, covalent bond, electrostatic interaction, van der waal interaction, hydrophobic interaction etc. It is commonly called as a domain.

The last level of folding of protein is the quaternary structure of protein. It is also stabilized by different types of covalent and noncovalent bonding. It is formed by the association of two or more domains.

Difference between globular and fibrous protein structures -

Globular proteins are mainly more compact and round in shape whereas fibrous proteins are elongated and narrow thread like structures.

Fibrous proteins have repetitive amino acid sequences whereas globular proteins have irregular amino acid sequences.

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