Step 3: Using protease to break down cellular proteins The...

Step 3: Using protease to break down cellular proteins The most prevalent class of molecules that would interfere with the precipitation of pure DNA is protein. We can easily get rid of protein without damaging the DNA by using a specific enzyme that digests proteins, called a protease. Protease breaks the peptide bonds between the amino acids of proteins. By destroying all the proteins you will also eliminate DNases, enzymes that digest DNA (because enzymes are proteins). FOCUS QUESTIONS 8. What proteins might be associated with DNA in the cell? 9. The protease used in this procedure functions best at 50°C. Would you expect this enzyme to be isolated from E. coli bacteria? Explain your answer. Hint: Where does E. coli live? 10. Meat tenderizer is often used to tenderize tough pieces of meat, like steak. Knowing that steak is made of protein-rich muscle tissue from cows, can you think of an explanation for how meat tenderizer works?

Transcript

00:01 Hello everyone, in this question we have been asked that what proteins might be associated with the dna in the cell.

00:10 So, we know that the dna has the negative charge present on it due to the phosphorus group attached at the carbon number 5 of the ribose group.

00:25 So, this dna is scattered in the cell and for it to be kept organized this needs to be wrapped around a protein.

00:35 So, this will only be attracted to a protein which has a positive charge.

00:42 So, there is a protein which is known as histone, in this there is positive charge because it is a basic protein.

00:53 It has abundant lysine and arginine in its core amino acid residue due to which it attracts to the dna.

01:03 So, let us say these here are the histone molecule, the dna are wrapped around the dna, around these histones proteins like this.

01:15 Inside the core there is h3h4 tachymer h2a and h2b diamond and there is one h1 histone that is the linker histone which links the two nucleosome.

01:31 This portion here is known as the nucleosome and this binds to the acidic phosphate group that is present on the dna.

01:42 So, the dna is associated with this histone so that they can get packaged into a more organized manner.

01:53 So, this histone helps in tight packaging of dna and forms the structure which is known as chromatid and then there is thousand times more folding and then a chromosome structure is obtained and for the catalytic action also this protein is linked with the dna.

02:15 There are certain non -histone proteins also like the histone like the high mobility group.

02:26 These are associated with dna and are non -histone chromosomal proteins and these induce the structural change in the chromatin fiber.

02:40 So, in this way the proteins are associated with the dna and this histone when it is tightly packed with the dna it does not undergo the transcription but this lysine is modified and if it is if it undergoes acetylation then the acetylation provides the negative removes this positive charge from the histone and that is why the dna becomes loose...

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