Extraterrestrial Protein?

Researchers Find Extraterrestrial Protein in Meteorite Acfer 086

A research team led by Harvard University scientist Julie McGeoch has found a never-before-seen protein inside a meteorite called Acfer 086.

A sample of Acfer 086. Image credit: McGeoch McGeoch, arXiv: 1707.09080.

Acfer 086 is one of a large collection of meteorites found in the Algerian Sahara desert.

The small space rock was found in Agemour, Algeria, in 1990 and weighed only 173 grams.

Acfer 086 is classified as a CV3 carbonaceous chondrite, and shows a low level of shock and a moderate degree of weathering.

In a new study, Dr. McGeoch and her colleagues from PLEX Corporation and Bruker Scientific LLC analyzed a sample of Acfer 086 from the Harvard Mineralogical and Geological Museum.

Using mass spectrometry, they detected the signal of an unusual iron- and lithium-containing protein.

Further analysis showed the new protein was mainly composed of glycine and hydroxyglycine amino acids.

“This is the first report of a protein from any extraterrestrial source,” the researchers wrote in their paper.

“Room temperature extracts from micron-sized meteorite particles contain polymers of amino acids with a definite chain length centered at 16 residues.”

“Analysis via iron and lithium isotope satellites in mass spectrometry reveals a novel protein motif with iron atoms closing out the ends of anti-parallel peptide chains composed of glycine.”

Model of the hemolithin molecule: space-filling mode (top), ball and stick (center), enlarged view of iron, oxygen and lithium termination (bottom). White = H; orange = Li; gray = C; blue = N; red = O and green = Fe. Hydrogen bonds are shown by dotted lines. Image credit: McGeoch et al, arXiv: 2002.11688.

Dubbed hemolithin, the newly-discovered protein is believed to have been created approximately 4.6 billion years ago.

“The principal indicator of extraterrestrial origin is an extreme raised D/H (deuterium/hydrogen) ratio that is revealed by close quantitative fitting of isotopic satellite peaks,” the scientists wrote.

“The average molecular deuterium excess above terrestrial is (25,700 ± 3,500)%₀, or a D/H ratio of (4.1 ± 0.5) x10^-3, comparable to cometary levels, interstellar levels and also equal to the highest prior report in micrometeorites.”

“Very high deuterium content indicates proto-solar disk or molecular cloud origin,” they added.

The team’s paper was posted on the arXiv.org preprint server in February 2020.

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Malcolm W. McGeoch et al. 2020. Hemolithin: a Meteoritic Protein containing Iron and Lithium. arXiv: 2002.11688