This article talks a little about the discovery of protein inside a meteorite found in 1990.
https://phys.org/news/2020-03-protein-meteorite.html
Protein found in a meteorite
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rdavidjohnson63
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Protein found in a meteorite
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Dale Smith
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Re: Protein found in a meteorite
Interesting.
Other links:
https://en.wikipedia.org/wiki/Hemolithin
http://astrobiology.com/2020/02/hemolit ... thium.html
The link you sent says “The hemolithin protein found by the researchers was a small one, and was made up mostly of glycine, and amino acids.” Glycine is an amino acid, so I suspect they meant to say “and other amino acids”. The Wikipedia article adds hydroxyglycine to the list. Hydroxyglycine is an amino acid, but it is not one normally found in proteins. (There are an enormous number of possible amino acids, but DNA, which provides the blueprints for making proteins, only codes for 20 amino acids.) The drawing of the structure actually shows two protein chains tied together at each end by the inorganic groups. As shown in the drawing each chain is 16 amino acids long with 13 glycines and 3 hydroxyglycines, but the chains are complimentary not identical. One chain looks like it was constructed in the order GGGGGGGGGGGHGHGH and the other in the order HGHGHGGGGGGGGGGG. If the chains were different lengths it would be harder to link both ends together in the manner shown.
The caption of the drawing says “Model of the 2320 hemolithin molecule after MMFF energy minimization.” I assume MMFF stands for Merck Molecular Force Field (a program for calculating molecular shapes). The Astrobiology article says ”Amino acid polymers previously observed in Acfer 086 and Allende meteorites [1,2] have been further characterized in Acfer 086 via high precision MALDI mass spectrometry to reveal a principal unified structure of molecular weight 2320 Daltons that involves chains of glycine and hydroxy-glycine residues terminated by iron atoms, with additional oxygen and lithium atoms.”
The phrase ‘principal unified structure’ implies there is a range of structures. I wonder how much deviation about the average structure there is. Is the structure as drawn an idealized average of a very messy range of structures or is the distribution very tight? It will be interesting to see the final peer reviewed version rather than short news blurbs.
I am afraid I do not share the author’s sentiment that this moves the ball much closer to showing how life came about.
There is a ‘chicken and egg’ nature to the relationship between DNA and proteins in living organisms. The function of DNA is to provide the template for making proteins (including the proteins used in the reading and replicating the DNA molecule). Proteins carry out the basic metabolic and structural processes of the cell, but generally cannot make copies of themselves. Even if we grant for the sake of argument the one in a googolplex chance of a diverse group of proteins with just the right mix of structural and catalytic properties, but no DNA, self-assembling into a living organism, how would it make more copies of those proteins as the originals wore out? How would it replicate to produce daughter cells? In the end such a cell would die childless. The end. Without DNA to record the protein sequences, the very many things this failed attempt got right would be lost forever. The search for Chapter 1 of the story of life would have to begin all over again from scratch. If this meteorite had also included DNA with the right sequence of bases to code for the hemolithin protein then I would get excited. As a chemist I find the hemolithin molecule interesting chemically, but by itself a very long way short of the origin of life.
The article also speculated that the ability to absorb light and use it to split water molecules could potentially be used by organisms as an energy source. That speculation requires a great deal of fleshing out. The devil is in the details. It is one thing for a chemical reaction to release energy. Capturing that energy in a way that can be used by other processes often involves at least an order of magnitude increase in the complexity of the system. For example, a gallon of gasoline can propel a car 20 miles or more. However, if I simply pour that gallon over my engine and set a match to it I will never get to the grocery store. Likewise, dumping lead pellets into a jar of sulfuric acid does not equal a car battery.
Other links:
https://en.wikipedia.org/wiki/Hemolithin
http://astrobiology.com/2020/02/hemolit ... thium.html
The link you sent says “The hemolithin protein found by the researchers was a small one, and was made up mostly of glycine, and amino acids.” Glycine is an amino acid, so I suspect they meant to say “and other amino acids”. The Wikipedia article adds hydroxyglycine to the list. Hydroxyglycine is an amino acid, but it is not one normally found in proteins. (There are an enormous number of possible amino acids, but DNA, which provides the blueprints for making proteins, only codes for 20 amino acids.) The drawing of the structure actually shows two protein chains tied together at each end by the inorganic groups. As shown in the drawing each chain is 16 amino acids long with 13 glycines and 3 hydroxyglycines, but the chains are complimentary not identical. One chain looks like it was constructed in the order GGGGGGGGGGGHGHGH and the other in the order HGHGHGGGGGGGGGGG. If the chains were different lengths it would be harder to link both ends together in the manner shown.
The caption of the drawing says “Model of the 2320 hemolithin molecule after MMFF energy minimization.” I assume MMFF stands for Merck Molecular Force Field (a program for calculating molecular shapes). The Astrobiology article says ”Amino acid polymers previously observed in Acfer 086 and Allende meteorites [1,2] have been further characterized in Acfer 086 via high precision MALDI mass spectrometry to reveal a principal unified structure of molecular weight 2320 Daltons that involves chains of glycine and hydroxy-glycine residues terminated by iron atoms, with additional oxygen and lithium atoms.”
The phrase ‘principal unified structure’ implies there is a range of structures. I wonder how much deviation about the average structure there is. Is the structure as drawn an idealized average of a very messy range of structures or is the distribution very tight? It will be interesting to see the final peer reviewed version rather than short news blurbs.
I am afraid I do not share the author’s sentiment that this moves the ball much closer to showing how life came about.
There is a ‘chicken and egg’ nature to the relationship between DNA and proteins in living organisms. The function of DNA is to provide the template for making proteins (including the proteins used in the reading and replicating the DNA molecule). Proteins carry out the basic metabolic and structural processes of the cell, but generally cannot make copies of themselves. Even if we grant for the sake of argument the one in a googolplex chance of a diverse group of proteins with just the right mix of structural and catalytic properties, but no DNA, self-assembling into a living organism, how would it make more copies of those proteins as the originals wore out? How would it replicate to produce daughter cells? In the end such a cell would die childless. The end. Without DNA to record the protein sequences, the very many things this failed attempt got right would be lost forever. The search for Chapter 1 of the story of life would have to begin all over again from scratch. If this meteorite had also included DNA with the right sequence of bases to code for the hemolithin protein then I would get excited. As a chemist I find the hemolithin molecule interesting chemically, but by itself a very long way short of the origin of life.
The article also speculated that the ability to absorb light and use it to split water molecules could potentially be used by organisms as an energy source. That speculation requires a great deal of fleshing out. The devil is in the details. It is one thing for a chemical reaction to release energy. Capturing that energy in a way that can be used by other processes often involves at least an order of magnitude increase in the complexity of the system. For example, a gallon of gasoline can propel a car 20 miles or more. However, if I simply pour that gallon over my engine and set a match to it I will never get to the grocery store. Likewise, dumping lead pellets into a jar of sulfuric acid does not equal a car battery.