Difference Between Motif and Domain

The key difference between motif and domain is that the motif is not independently stable while the domain is independently stable.

Proteins are important biological macromolecules present in our body. On the other hand, the genetic code of a gene will decide the amino acid sequence of a protein. Moreover, proteins have primary, secondary and tertiary structures. The primary structure is the amino acid sequence of the polypeptide chain. When polypeptide chains fold with each other, it forms the secondary structure of the protein. Alpha helices, beta sheets and super-secondary structures are belonging to the secondary structures. Certain groupings of super-secondary elements are known as protein motifs. The tertiary structure of a protein refers to its three-dimensional structure that decides the function of the protein. Domain is a folded section of a protein molecule, which is globular and has a discrete function. It is the fundamental functional and three-dimensional structure of the protein.

CONTENTS

1. Overview and Key Difference
2. What is Motif
3. What is Domain
4. Similarities Between Motif and Domain
5. Side by Side Comparison – Motif vs Domain in Tabular Form
6. Summary

What is Motif?

Motif is a certain grouping of the super secondary elements of proteins such as alpha helices and beta structures. They are some kind of patterns present in different proteins. Motifs describe the folding patterns of the secondary structural elements and their interactions. These folding patterns stabilize by similar linkages that are present in tertiary structures. However, they are not as complex as tertiary structures.

They are simple combinations of secondary structures of proteins. Motif is not stable by itself. Furthermore, motifs explain the structure of a protein but do not predict the function of a protein. Examples of protein motifs are a beta-alpha-beta motif, Greek key motif, Beta barrel, Beta-meander motif, etc.

What is Domain?

Domain is a fundamental, functional and three dimensional unit of a protein. It performs a particular function. A single protein can have several distinct domains. Each domain is an independent unit. It is a globular structure. It is responsible for a specific function or interaction. Domains can be used to hypothesize the function of an uncharacterized protein. When analyzing a protein, it is essential to take into account since domains are the functional units of the protein.

Domains are very stable and compact structures. They can be easily distinguished from other regions. Pyruvate kinase has three distinguish domains as shown in figure 02. The length of the domain can vary, and the average length is 100 amino acids. Each domain contains a hydrophobic core built from secondary structural units. Several domains collectively make the tertiary structure of a protein.

What are the Similarities Between Motif and Domain?

• Motif and domain are units present in protein molecules themselves.
• They are useful when classifying protein families.

What is the Difference Between Motif and Domain?

Motif is a certain grouping of the super secondary elements of proteins such as alpha helices and beta structures while domain is the functional unit of a protein. Furthermore, motif is a secondary structure while domain is responsible for the tertiary structure of the protein. Moreover, domain is an independent unit, unlike a motif. Also, domain depicts the function of a protein while motif is not. These are the main differences between motif and domain. The below infographic presents the difference between motif and domain in tabular form.

Summary – Motif vs Domain

Motif is an arrangement of secondary structures of the protein molecule. It is not usually stable by itself, unlike a domain. Domain is an independently stable structure of a protein. Therefore, it can be a part or whole protein molecule. It is a three dimensional fundamental functional unit of the protein. Moreover, it has a function, and it is an independent unit. Motif can be a part of the domain. But domain cannot be a part of a motif. This is the difference between motif and domain.

Reference:

1.“Protein Domain.” Wikipedia, Wikimedia Foundation, 31 July 2018. Available here

Image Courtesy:

1.”Anthrax toxin protein key motif”By NatelewisDerivative work (CC BY-SA 3.0) via Commons Wikimedia
2.”Pyruvate kinase protein domains”By Thomas Splettstoesser – Own work, (CC BY-SA 3.0) via Commons Wikimedia