Question

Protection required. Suppose that a mutation in bacteria resulted in the diminished activity of methionine adenosyltransferase, the enzyme responsible for the synthesis of SAM from methionine and ATP. Predict how this diminished activity might affect the stability of the mutated bacteria's DNA.

Short answer

Reduced SAM levels due to diminished enzyme activity can lead to DNA methylation defects, destabilizing the bacterial genome.

Step-by-step solution

What is Methionine Adenosyltransferase?

Methionine adenosyltransferase is an enzyme responsible for catalyzing the conversion of methionine and ATP (adenosine triphosphate) to S-adenosylmethionine (SAM). SAM is a key methyl donor in numerous methylation reactions in cells.

Understand the Role of SAM in DNA Methylation

SAM is crucial because it acts as a major methyl donor in the methylation of DNA. Methylation of DNA is essential for regulating gene expression and maintaining genomic stability. Without adequate SAM, proper methylation patterns cannot be maintained.

Consequence of Diminished Methionine Adenosyltransferase Activity

If the activity of methionine adenosyltransferase is diminished, the synthesis of SAM will be reduced. This leads to a decrease in the availability of SAM for methylation reactions.

Predict the Impact on DNA Stability

With reduced SAM levels, DNA methylation processes are disrupted. This can result in improper DNA methylation patterns, potentially leading to genomic instability and increased susceptibility to mutations.

Key concepts

Methionine Adenosyltransferase

Methionine adenosyltransferase plays a crucial role in the methylation process in organisms. This enzyme is responsible for facilitating the reaction that combines methionine, an essential amino acid, with ATP to form S-adenosylmethionine (SAM). SAM is the principal methyl group donor in numerous biological processes, including DNA methylation. Methionine adenosyltransferase ensures there is a sufficient supply of SAM for these methylation reactions. Without adequate function of this enzyme, the levels of SAM could be significantly reduced, impacting many cellular activities. It is important because many of these activities, particularly DNA methylation, are vital for cell regulation and stability.

S-adenosylmethionine (SAM)

SAM is known as the universal methyl donor because it contributes its methyl group to a variety of biological reactions, including DNA methylation, RNA processing, protein methylation, and lipid metabolism. In the process of DNA methylation, SAM donates its methyl group to cytosine bases in DNA, which leads to the formation of 5-methylcytosine.
This modification is critical in regulating gene expression, as it can turn genes on or off. Furthermore, SAM plays a role in stabilizing the structure of DNA, thus maintaining genomic integrity. If SAM levels are low due to impaired methionine adenosyltransferase function, the methylation processes become compromised. This can lead to numerous downstream effects that disrupt normal cellular function.

Genomic Stability

Genomic stability refers to the maintenance and integrity of a genome over time, ensuring that the genetic information is preserved and faithfully transmitted during cell division. It's crucial for healthy cell function and for preventing diseases like cancer. A key factor in maintaining genomic stability is the proper methylation of DNA.
DNA methylation, facilitated by SAM, helps regulate the expression of genes and maintains the structure of chromatin, which is how DNA is packaged in the cell nucleus. Proper methylation patterns ensure that genes are expressed at the right time and in the right amount. However, diminished activity of methionine adenosyltransferase can reduce SAM levels, leading to defective methylation patterns.

• This disruption can make the genome more susceptible to mutations and rearrangements, potentially causing cellular dysfunction and contributing to disease progression.
• Maintaining genomic stability through proper methylation is essential for the longevity and health of an organism.