Membrane Channel Lets Only Some Ions in

Biological Strategy

Streptomyces

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Capture, Absorb, or Filter Chemical Entities

Living systems often require chemical elements and chemical compounds, including complex sugars, proteins, and odor-making compounds, to perform critical activities. These compounds exist in various states–solid, liquid, and gas–and are ubiquitous in soil, water, and air. This requires that living systems not only have ways to capture, absorb, or filter them, but also ways to differentiate among them, selecting those that are valuable or harmful. For example, mangrove trees live with their roots in salty water and sediments. Various mangrove species have different strategies for removing salt from the water they take in so that their tissues can use the fresh water.

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Bacteria

Domain Bacteria (“small staff”): L. acidophilus, Staphylococcus

From inside of our own bodies to the deepest parts of the ocean, bacteria have adapted to almost every possible environment. All bacteria are unicellular, microscopic, and lack a membrane-bound nucleus and organelles, and come in three basic shapes: spherical (cocci), rod (bacilli), and spiral (spirilla). Some strains can be deadly, like Staphylococcus aureus (MRSA) while others, like Lactobacillus acidophilus, found in our intestinal microbiome, keep us healthy. Cyanobacteria, also known as blue green algae, caused the Great Oxidation Event 2.4 billion years ago, producing Earth’s first oxygenated atmosphere.

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The membrane of Streptomyces lividans cells lets potassium ions in but not sodium via a potassium-specific channel.

“The researchers cracked the structure of the through a technique called X-ray crystallography, and it then became clear how the channel would admit potassium ions only, even though closely-related sodium ions were even smaller. The structural analysis showed the channel is lined by oxygen atoms that mimic the water cluster normally surrounding a potassium ion in aqueous solution. Sodium has a slightly different water shell, and so cannot fit through the channel. The analysis also revealed parts of the protein that receive ‘on’ and ‘off’ chemical signals.” (Coghlan 2003)

Last Updated August 18, 2016

References

Journal article

Chemistry Nobel winner: My work is not done

New Scientist | 18/10/2010 | Andy Coghlan

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Reference

Journal article

Chemistry Nobel rewards crucial cell membrane work

Andy Coghlan

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