Harvard team claims to find 'Hemolithin' protein series on asteroid

[.Scott]

TL;DR

Harvard researchers believe they have found protein inside a 1989 meteorite.

A Harvard teams believe they have found a protein series they call "Hemolithin" in an asteroid.
Isotopes and other evidence indicates that it is not from a terrestrial source."Astrobiology Web" link
arxiv pdf link

Structures are presented in S5 for each of these. 2320 and 2364 have 32 amino acid residues while 2124 has 30. An additional 34 amino acid structure at 2402 is also proposed in S5, to fit two peaks within the 4641Da cluster. The chain lengths in each anti-parallel configuration are therefore 16 residues for 2320 and 2364, 15 residues for 2124 and 17 residues for 2402. As discussed herein the glycine residues are subject to varying degrees of hydroxylation, but the more constant parameter is the number of glycines per side. We propose calling the 16-residue entity Hemolithin 16, and the 15 or 17-residue entities Hemolithins 15 or 17.

 

[Ygggdrasil]

It is somewhat of a stretch to call these proteins. Proteins are typically much longer polypeptide chains. For example, the Wikipedia entry for proteins says "Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides, or sometimes oligopeptides."

Still, this is an interesting finding that, if true, could provide pretty strong evidence for abiotic polypeptide formation and influence how we thing about the potential origin of life on Earth.

 

[jim mcnamara]

@Ygggdrasil

FWIW -
In this thread
https://www.physicsforums.com/threads/science-white-paper-on-miniproteins.979258/

There is a category of short and redundant amino acids sequences called miniproteins that are biologically active.
White paper:
https://www.sciencemag.org/news/2019/10/new-universe-miniproteins-upending-cell-biology-and-genetics

Assuming the hemolithin paper is not the result of an artifact, short sequences like this would reasonably be expected to arise in the course of the evolution of more complex proteins. I am not so sure about the presence of the Lithium atom in the results. The mass fraction of Lithium is way down the list of elements ordered by abundance in the Universe, ditto the Solar System.

 

[.Scott]

Assuming the hemolithin paper is not the result of an artifact, short sequences like this would reasonably be expected to arise in the course of the evolution of more complex proteins.

The "evolution of more complex proteins" suggests a Darwinian selection process. Just to be clear, no one is suggesting that this particular protein, or mini-protein, or polypeptide was the result of DNA, RNA, or any other kind of replication process. So it's potential to "evolve" is really limited.

 

[jim mcnamara]

What I tried to say, not very well obviously, is that protein abiogenesis (synthesis) had to start small.

Miniproteins are the 'leftovers' of that early synthetic step. Procaryotes and Eukaryotes still employ them for other uses. I'm citing the minprotein paper as much as anything. And using the homeolithin molecule as supportive for what the miniprotein paper claims. In a loose sense they are a "fit". By no means anything conclusive.

I try for perspective, or insight, pick a name... because most PF'ers are not Biologists. It backfires sometimes. Sorry.

 

[Ygggdrasil]

@Ygggdrasil

FWIW -
In this thread
https://www.physicsforums.com/threads/science-white-paper-on-miniproteins.979258/

There is a category of short and redundant amino acids sequences called miniproteins that are biologically active.
White paper:
https://www.sciencemag.org/news/2019/10/new-universe-miniproteins-upending-cell-biology-and-genetics

Assuming the hemolithin paper is not the result of an artifact, short sequences like this would reasonably be expected to arise in the course of the evolution of more complex proteins. I am not so sure about the presence of the Lithium atom in the results. The mass fraction of Lithium is way down the list of elements ordered by abundance in the Universe, ditto the Solar System.

I guess I have two problems with the authors' characterization of the peptides as proteins:
1) The term protein implies that it is a molecule of biological origin, which has not yet been shown.
2) As you mention above, the term protein also implies some biological activity or function, which also has not yet been established.

Calling the molecules peptides or polypeptides would not carry these biological implications and, in my opinion, would be a better label for their findings.