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> Anthropomorphizing such things is a silly because it confuses people The rest of my post gave a very high-level explanation of how a virus infects a human ce

by jforman 16y ago

> Anthropomorphizing such things is a silly because it confuses people The rest of my post gave a very high-level explanation of how a virus infects a human cell. To explain it in full would take many hours verbally (it took me months in my program to even get up to speed on molecular biology, having come from a CS background). I'll give some more detail, though: when I say "specifically tuned to human physiology" I mean "tuned" to an extreme level. A human cell is a bag of water, protein, and nucleic acids enveloped by a lipid bilayer. This lipid bilayer physically prevents anything larger than...I think a subset of very small molecules from entering the cell? I am very weak in biochem, so I don't know the exact parameters around this, but I do know for certain that a virus is many orders of magnitude too large to just "get in" to a cell. In order to gain entry to the cell, the virus has to have a protein that is extremely specifically targeted to a human protein that sits on the surface of a human cell. Like, antibody-to-antigen level specific - this is the product of many many generations of evolution. After attaching to that protein, the virus performs a very biochemically specific action to inject its payload into the cell. > Their folding state _is_ the infection mechanism Er, not really. It's the infection mechanism once the prion is in the cell (since the proteins to which the infection spreads are in a cell). How does the protein get in the cell in the first place? ...that's what nobody knows. It can't just float in, again because of the lipid bilayer. It needs to be actively pulled into the cell. Why would that happen?

rdtsc 16y ago
> After attaching to that protein, the virus performs a very biochemically specific action to inject its payload into the cell. So? If a simple misconfigured protein can enter the cell without the complicated and specifically tuned machinery and is able to proliferate that way, isn't it more advanced. I would say so I presume you are an engineer, so I'll make the assumption that you are quite fond of "complciated" things and assume them to be supperior to simpler things. But if both accomplish the same thing, should you consider the simpler thing to be supperior? I do. > Er, not really. I think we can agree as to what prions are -- misconfigured proteins. If we can agree that there is nothing more besides that, how is the folding state _not_ the infection mechanism. I am not talking about what the cell does, just what what is considered the transmitted -- the prion itself. > ...that's what nobody knows. Er, not really. They have some pretty good guesses. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0003314 http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjourna... """ How, then, does prion protein enter cells? It turns out to be by a mechanism called macropinocytosis. This involves the invagination and pinching off of a segment of cell membrane, and is used by cells to take up small amounts of liquids (macropinocytosis means "big cell drinking"). """ Also: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC165614/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC165614/ """ While still on the cell surface, prion protein leaves lipid ‘raft’ domains to enter non-raft membrane, from which it enters coated pits. The N-terminal domain (residues 23–107) of prion protein is sufficient to direct internalization, an activity dependent upon its initial basic residues (NH2-KKRPKP). """

by jforman 16y ago

rdtsc 16y ago

> After attaching to that protein, the virus performs a very biochemically specific action to inject its payload into the cell. So? If a simple misconfigured protein can enter the cell without the complicated and specifically tuned machinery and is able to proliferate that way, isn't it more advanced. I would say so I presume you are an engineer, so I'll make the assumption that you are quite fond of "complciated" things and assume them to be supperior to simpler things. But if both accomplish the same thing, should you consider the simpler thing to be supperior? I do. > Er, not really. I think we can agree as to what prions are -- misconfigured proteins. If we can agree that there is nothing more besides that, how is the folding state _not_ the infection mechanism. I am not talking about what the cell does, just what what is considered the transmitted -- the prion itself. > ...that's what nobody knows. Er, not really. They have some pretty good guesses. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0003314 http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjourna... """ How, then, does prion protein enter cells? It turns out to be by a mechanism called macropinocytosis. This involves the invagination and pinching off of a segment of cell membrane, and is used by cells to take up small amounts of liquids (macropinocytosis means "big cell drinking"). """ Also: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC165614/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC165614/ """ While still on the cell surface, prion protein leaves lipid ‘raft’ domains to enter non-raft membrane, from which it enters coated pits. The N-terminal domain (residues 23–107) of prion protein is sufficient to direct internalization, an activity dependent upon its initial basic residues (NH2-KKRPKP). """