A Year of (Bio)chemical Elements

Manganese seldom travels alone

Quira Zeidan
Sept. 1, 2019

We mark the 150th anniversary of Dimitri Mendeleev’s periodic table of chemical elements this year by highlighting elements with fundamental roles in biochemistry and molecular biology. So far, we’ve covered hydrogen, iron, sodium, potassium, chlorine, copper, calcium, phosphorus, carbon, nitrogen and oxygen.

Manganese ribbon diagramThis ribbon diagram represents the structure of the human superoxide dismutase 2 tetramer in coordination with four manganese ions shown in violet.Fvasconcellos/Wikimedia Commons

For September, we describe manganese, a transition metal with chemical symbol Mn and atomic number 25. Manganese is highly reactive, and it almost never is found as a free element in nature. Rather, it combines with other elements via its multiple oxidation states, which range from +7 to -3. It frequently is found in silicate, carbonate and oxide minerals, and in alloys — compounds containing metals — with iron. People used manganese-containing pigments that are naturally abundant in cave paintings dating back to the Stone Age.

Nuclear reactions that occur in giant stars immediately before supernova explosions produce manganese. It has a short half-life of about 3.7 million years and decays into one of the four chromium isotopes — element variants with different numbers of neutrons. At 0.1%, manganese is the 12th most abundant element on the Earth’s crust. A significant amount of manganese is present on the ocean floor in the form of manganese nodules — specific marine deposits composed by manganese hydroxide and iron.

In living systems, manganese chemistry is restricted to Mn+2 and Mn+3 ions that combine with biological molecules in the aqueous environment of the cell. Mn+2 often overlaps and competes with magnesium and calcium ions as a structural component that stabilizes the net charge of molecules such as proteins and adenosine triphosphate. As a redox cofactor for a large variety of enzymes, manganese is at the catalytic center for cellular reactions that participate in aerobic metabolism.

Manganese is vital to microbial survival. Protein transporters in bacteria break down high-energy chemical bonds in adenosine triphosphate to drive the influx of manganese into the cell from the extracellular environment. Bacterial species of the normal flora of the human digestive and reproductive systems require manganese for survival and growth. The Lyme disease pathogen Borrelia burgdorferi can incorporate manganese in all of its metalloproteins, bypassing host defense by eliminating the need for iron. The diphtheria toxin secreted by the pathogen Corynebacterium contains manganese in its structure. Some bacteria use nonenzymatic Mn+2 ion complexes — generally in combination with polyphosphate — to scavenge reactive oxygen species that are byproducts of cellular metabolic reactions.

In yeast and other eukaryotes, the natural resistance-associated macrophage protein, or NRAMP, family of metal transporters uptake manganese using the driving force of proton gradients. Once inside cells, manganese serves as a cofactor for a multitude of enzymes that include oxidoreductases, carbohydrate-binding proteins such as lectins, and extracellular matrix receptors such as integrins.

Superoxide dismutase, an important manganese-containing enzyme present in mitochondria — and in most bacteria — partitions harmful reactive superoxide ions into molecular oxygen or hydrogen peroxide, protecting cells from the toxicity associated with aerobic respiration. In plants and cyanobacteria, manganese is an essential component of the enzyme responsible for the terminal oxidation of water during the light reactions of photosynthesis.

Enjoy reading ASBMB Today?

Become a member to receive the print edition four times a year and the digital edition weekly.

Learn more
Quira Zeidan

Quira Zeidan is the ASBMB’s education and public outreach coordinator.

Get the latest from ASBMB Today

Enter your email address, and we’ll send you a weekly email with recent articles, interviews and more.

Latest in Science

Science highlights or most popular articles

From lab to land: Crop modifications are fortifying our food supply against climate change
News

From lab to land: Crop modifications are fortifying our food supply against climate change

Nov. 13, 2024

Scientists explore genetic and biochemical innovations fueling future-proofing agriculture

Join the pioneers of ferroptosis at cell death conference
In-person Conference

Join the pioneers of ferroptosis at cell death conference

Nov. 13, 2024

Meet Brent Stockwell, Xuejun Jiang and Jin Ye — the co-chairs of the ASBMB’s 2025 meeting on metabolic cross talk and biochemical homeostasis research.

How antioxidant-enhanced ice cream is changing the game for frozen treats
News

How antioxidant-enhanced ice cream is changing the game for frozen treats

Nov. 12, 2024

University of Wisconsin scientists create a sweet treat with more nutrients and better stability using tannins

Helping underrepresented scientists feel seen
Award

Helping underrepresented scientists feel seen

Nov. 12, 2024

Benjamin Garcia will receive the ASBMB Ruth Kirschstein Diversity in Science Award at the ASBMB Annual meeting, April 12–15 in Chicago.

Plants get a GMO glow-up
News

Plants get a GMO glow-up

Nov. 10, 2024

Lose the prickles. Add bioluminescence. Up the nutrients without the bitter flavor. CRISPR gene editing is opening a new world of genetically modified plants for home growers.

Bananapocalypse – the tricky genetics of a devastating fungus
News

Bananapocalypse – the tricky genetics of a devastating fungus

Nov. 9, 2024

Fusarium oxysporum can infect over 120 plant species. Whether it destroys Cavendish bananas as it did their predecessor depends on the agricultural industry and consumers.