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Archaeal ribosomes are like eukaryotic not bacterial forms

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1378332.  Fri Apr 02, 2021 10:26 am Reply with quote

That's not exactly accurate but basically the ribosomes of archaea exhibit features in common with eukayotes which are not present in bacteria.

This has substantial importance regarding the early evolution of life - specifically we are at least partially descended from archaea - or rather some form of proto-archaea!

Thus proponents of symbiogenesis

Symbiogenesis, endosymbiotic theory, or serial endosymbiotic theory is the leading evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms. The theory holds that mitochondria, plastids such as chloroplasts, and possibly other organelles of eukaryotic cells are descended from formerly free-living prokaryotes (more closely related to bacteria than archaea) taken one inside the other in endosymbiosis.

are wrong at least to that extent (and for my money in further regards too).

post 1088121

...this and other analyses strongly support an archaeal origin for a substantial fraction of the eukaryotic translational machinery, especially the ribosomal proteins, there have been numerous unique and ubiquitous additions to the eukaryotic translational system besides the 11 unique eukaryotic ribosomal proteins. These include peptide additions to most of the 67 archaeal homolog proteins, rRNA insertions, the 5.8S RNA and the Alu extension to the SRP RNA. Our comparative analysis of these and other eukaryotic features among the three different cellular phylodomains supports the idea that an archaeal translational system was most likely incorporated by means of endosymbiosis into a host cell that was neither bacterial nor archaeal in any modern sense. Phylogenetic analyses provide support for the timing of this acquisition coinciding with an ancient bottleneck in prokaryotic diversity.
The archaeal origins of the eukaryotic translational system
Hyman Hartman, Paola Favaretto, and Temple F. Smith
Archaea. 2006 Aug; 2(1): 19.
Published online 2005 Nov 9.

1378333.  Fri Apr 02, 2021 10:58 am Reply with quote

This is the kind of stuff on University Challenge I tend to gloss over :)

1378334.  Fri Apr 02, 2021 11:35 am Reply with quote

Just as well I didn't start writing about the rising confidence regarding the Cisternal Maturation Model of Golgi function then.

1378338.  Fri Apr 02, 2021 4:26 pm Reply with quote

That sounds like something out of an H P Lovecraft book.

1378340.  Fri Apr 02, 2021 4:51 pm Reply with quote

I had a similar thought the first (and to be honest every subsequent) time I read about Dankwerts' Surface Renewal Theory. It sounds like something from a medieval grimoire - if you stumble across a likely candidate in a neglected corner of a New England library please tell me all about it.

In truth it's more like the form of names given to FRP spells invented by the initial players of the game - Mordenkainen's Faithful Hound for example; the character Mordenkainen was played by E. Gary Gygax himself way back before the game was released commercially.

Quite what the spell Cisternal Maturation of Golgi would do is an interesting question - one meaning of maturation is the development of pustules so that's a promising start!

1378367.  Sat Apr 03, 2021 5:48 am Reply with quote

Tbh, most of the OP looked to me like someone had dropped a box of Scrabble tiles.....

1378374.  Sat Apr 03, 2021 7:06 am Reply with quote

crissdee wrote:
Tbh, most of the OP looked to me like someone had dropped a box of Scrabble tiles.....

Most of the words are too long for Scrabble!

By the way, did you know that "eukaryotic" contains each vowel once and only once - irrespective of whether you count "y" as a vowel or not?

(Sorry, that's about as relevant as I can get.)

1378375.  Sat Apr 03, 2021 7:06 am Reply with quote

Good Morning Vietnam - abbreviation scene

1378389.  Sat Apr 03, 2021 2:23 pm Reply with quote

I must rewatch that movie!

1378403.  Sun Apr 04, 2021 1:47 am Reply with quote

As I travel further down this particular rabbit-hole more and more jaw-dropping stuff appears out of the murk; for instance

Archaeal membrane lipids look very, very different from both bacteria and from eukaryotes (top molecule, above). [The membrane phospholipids of] Archaea have tails built of units of the branched chemical isoprene instead of fatty acids, and their 20-carbon tails are called phytanyl groups (I nominate phytanyl for Vowel Efficient Word of the Week).

...archaeal and bacterial enzymes use glycerols with opposite handedness* [this] implies that bacteria and archaea parted ways long, long ago.

* opposite chirality! This is a huge deal@

No obviously parasitic or pathogenic archaea have ever been found.

There are two possible forms of the molecule that are mirror images of each other. It is not possible to turn one into the other simply by rotating it around. While bacteria and eukaryotes have D-glycerol in their membranes, archaeans have L-glycerol in theirs. This is more than a geometric difference. Chemical components of the cell have to be built by enzymes, and the "handedness" (chirality) of the molecule is determined by the shape of those enzymes. A cell that builds one form will not be able to build the other form.

The most striking chemical differences between Archaea and other living things lie in their cell membrane. Their are four fundamental differences between the archaeal membrane and those of all other cells: (1) chirality of glycerol, (2) ether linkage, (3) isoprenoid chains, and (4) branching of side chains.

That the membranes of eg mitochondria are not archaeal in origin but their ribosomes essentially are (they must be if current thinking is correct - though evolved to efficiently fill the role of an obligate endosymbiont) raises some questions as it is difficult to imagine how a change in membrane type could be a) gradual or b) result from a single mutation event but not be catastrophic in terms of membrane protein function.

With this in mind I shall continue my cunicular explorations at a later point.

Last edited by Celebaelin on Sun Apr 04, 2021 9:56 am; edited 1 time in total

1378409.  Sun Apr 04, 2021 3:52 am Reply with quote

Brock wrote:
By the way, did you know that "eukaryotic" contains each vowel once and only once - irrespective of whether you count "y" as a vowel or not?

And facetious has all five vowels in alphabetical order.

1378410.  Sun Apr 04, 2021 4:04 am Reply with quote

Awitt wrote:

And facetious has all five vowels in alphabetical order.

"Facetiously" would give you the "y", of course.

1378463.  Sun Apr 04, 2021 3:31 pm Reply with quote


and I'm not sure why cel is so excited about this information - which probably means I don't understand it

1378483.  Sun Apr 04, 2021 8:21 pm Reply with quote

bobwilson wrote:
I'm not sure why cel is so excited about this information - which probably means I don't understand it

Until relatively recently we weren't even aware archaea existed; the proposition that archaea are a third domain of the classification of all life was fiercely resisted when it was first suggested in 1977 (as most new ideas are irrespective of whether they are correct or not) and is still mentioned more or less as an afterthought because even now 45 years or so later relatively little is known about archaea and some continue to argue that they and eukatyotes are two divisions of a single branch. The perception of them as extremophile oddities persists whereas they have been found to be ubiquitous and will I imagine continue to surprise us with their role in the ecology and evolution of life on this planet as a whole.

The realisation that they are very probably responsible for one of the earliest steps in the development of eukaryotic cells (i.e. you, me, 'higher' plants and animals, most multicellular organisms whether plant or animal and quite a number of single celled organisms too) is a big deal.

The similarities in form between eukaryotic ribosomes and those of archaea are very unlikely to be co-incidental so eukaryote translational biochemistry (the way we make proteins from a nucleic acid messenger template) is almost certainly borrowed from archaea. Personally I think the possibility of transformation/transfection of a proto-eukaryote with free DNA from cell lysis is at least as likely as endocytosis of another cell in toto irrespective of whether that DNA was archaeal or bacterial in origin. The nucleus itself has been postulated as another example of a sub-cellular structure that has evolved from the endocytosis of an archaeal cell - the similarity between, and indeed presence of, histones in archaea and eukaryotes but not bacteria is cited as evidence for this. I'm a bit skeptical and tend towards the opinion that again DNA uptake is a simpler and therefore, according to Occam and to Aristotle before him, more likely explanation. I therefore feel that these multiple endocytosis events are not required to explain our observations of sub-cellular structures and organelles. I shan't hold my breath while waiting to find published support for this notion but the eukaryotic cell does have a characteristic tendency to compartmentalise its products and functions within membranes (e.g. vesicles, lysozymes, protein bodies etc.) thus increasing local concentrations and allowing for the evolutionary advantage of being able to better control the rate of movement of cellular constituents and metabolic intermediates away from their site of synthesis to a designated target - so I like my idea but then again I would wouldn't I?

It's important not to get brow-beaten by those who just point-blank refuse to consider the possibility that endocytosis and subsequent symbiogenesis may not be the answer - but then again I've never really believed that suggestion so in truth I'm sticking with my pre-suppositions as well however I'm clearly right about this as I always am.

1378598.  Tue Apr 06, 2021 8:02 am Reply with quote

I'm loving that you're excited by this, and I think if I had more time and energy at the moment to properly read and understand, I would share your enthusiasm, but at the moment it's gone completely over my head.

Don't let mine (and others) lack of understanding deter you.


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