Chapter 18.3, Problem 8SAQ

Summary Introduction

To determine:

The change in the binding of large multisubunit protein when it binds to a small molecule no larger than one amino acid.

Introduction:

In genetic diversity the gene may be regulated in two directions one is negative regulation and other is positive regulation. To carry out the process of transcription and translation we need the main player such as DNA, RNA polymerase, and regulatory proteins which are together called as transcriptional activator. The function of activator protein involves the binding to DNA specific sequence. But sometimes it happens that the activator protein binds to the small protein molecules that alter its binding affinity for DNA.

Explanation of Solution

When the large protein molecule binds with a small molecule of protein it leads to conformational change in the part of protein. The binding affinity of the protein alters due to change in the shape and this shows allosteric effect. Sometimes small molecules are needed for the binding of proteins to a particular sequence of DNA as it allows the change in the shape of activator protein. Thus the presence of small molecules regulates the transcription of gene. The combination of small molecule to a large protein brings structural change and its specificity for the original DNA binding site changes. It generates a new and different DNA binding specificity due to exposure of a new amino acid chains.

Conclusion

The binding of small molecule to a larger and multisubunit protein results in the structural change of protein. This results in the alteration of the amino acid change and thus the specificity for DNA binding site changes. Sometimes small molecule play significant role for binding of the protein molecule to a specific DNA sequence.