Description

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Picture Courtesy: THE HINDU

Context:

CSIR-Centre for Cellular and Molecular Biology (CCMB) researchers discover lipids play a crucial role in guiding evolution, alongside DNA and proteins.

Background

Scientists have long believed that DNA mutations change proteins, driving evolution. Lipids, which make up about 30% of a cell’s dry weight, were seen as passive “packing material” in cell membranes. However, recent research proves that lipids actively participate in evolution, co-evolving with proteins to help organisms survive.

Study focuses on Respiratory Complex 1 (RC1)

RC1 is a large protein complex in the mitochondrial inner membrane, crucial for producing energy during respiration (when cells use oxygen). It has three parts:

Part 1: Inside the mitochondria, it catalyzes reactions for energy.
Part 2: Embedded in the membrane, it channels hydrogen ions.
Part 3: Extends into the space between mitochondrial membranes; its role is less clear.

Key Findings of the Study

Kingdom-Specific Lipid-Protein Interactions

Plant v/s Animal Lipids: Plants and animals have different lipid structures. Plant lipids, rich in polyunsaturated fatty acids, have “kinkier” tails, making membranes more flexible. Animal lipids are less kinky, suited to their environments.
Lipid-Protein Match: Using computational models, the team shows that human RC1 proteins work best with human lipids, and plant RC1 proteins prefer plant lipids. This specificity indicates a deep connection between lipids and proteins.
Cardiolipin, a key mitochondrial lipid, varies between kingdoms. Human cardiolipin supports human RC1, while plant cardiolipin supports plant RC1.

Proof of Lipid-Protein Co-Dependence

Lab Experiment: When researchers insert plant RC1 parts into human mitochondrial membranes, the RC1 complex falls apart. This shows RC1 needs lipids from the same kingdom (plant or animal) to stay intact. Lipids aren’t just passive; their structure determines which proteins can function, influencing cell survival.

Evolutionary Importance

Lipids evolved to meet survival needs. For example; plant lipids’ kinky structure likely developed to handle environmental stresses like drought, heat, or salinity, giving membranes flexibility. Proteins like RC1 evolved alongside lipids to maintain compatibility. This lipid-protein co-evolution ensures cells function properly in different organisms.

Significance

Scientific Impact

Rewrites Textbooks: This study challenges the protein/DNA focus of evolution, urging scientists to include lipids in evolutionary models.
Supports Other Research: It aligns with studies showing lipid-protein interactions in other membranes, like those in bacteria or cancer cells. It calls for a broader view of cellular evolution, considering multiple molecules (DNA, proteins, lipids).

Medical Applications

Lipid-Related Drugs: Understanding lipid-protein interactions could improve drugs like statins, used to control cholesterol. Statins affect lipid levels, and this research may optimize their long-term use.
Pathogen Control: Lipids influence how pathogens (e.g., viruses, bacteria) enter cells. This study suggests new ways to block pathogen entry by targeting lipids, potentially leading to novel treatments.
Disease Insights: RC1 mutations linked to lipid interactions cause mitochondrial diseases. This research could guide treatments for such conditions.

Environmental and Agricultural Applicability

Plant Adaptability: The flexible structure of plant lipids helps plants survive harsh conditions. This knowledge could inform crop engineering for climate resilience.
Biodiversity: Understanding kingdom-specific lipid evolution deepens our knowledge of why plants and animals differ, relevant for biodiversity conservation.

Source:

THE HINDU

PRACTICE QUESTION

Q. In the question given below, there are two statements marked as Assertion (A) and Reason (R). Mark your answer as per the codes provided:

Assertion (A): Lysosomes are often referred to as the "suicidal bags" of the cell.

Reason (R): They contain hydrolytic enzymes that can digest cellular components.

Which of the options given below is correct?

A) Both A and R are true, and R is the correct explanation for A.

B) Both A and R are true, but R is not the correct explanation for A.

C) A is true, but R is false.

D) A is false, but R is true.

Answer: A

Explanation:

Assertion (A) is true: Lysosomes are called the "suicidal bags" of the cell due to their function in intracellular digestion and their potential to release enzymes that can lead to cell breakdown.

Reason (R) is true: Lysosomes contain a variety of powerful hydrolytic enzymes (enzymes that break down molecules using water) that are capable of digesting cellular components, including proteins, nucleic acids, carbohydrates, and lipids.

Reason (R) correctly explains Assertion (A): The presence of these digestive enzymes within lysosomes is the very reason why they are referred to as "suicidal bags." If the lysosomal membrane ruptures, these enzymes can be released into the cytoplasm, leading to the digestion of the cell's own components. This process is involved in programmed cell death (apoptosis) and the breakdown of damaged organelles.