4 ms·

Basic biochemistry question (you can tell what I didn't study in uni) Is it possible to mix chirality in, say, a protein? I.e. have a portion of one chirality

by ethbr1 2y ago

Basic biochemistry question (you can tell what I didn't study in uni) Is it possible to mix chirality in, say, a protein? I.e. have a portion of one chirality and another of the other?

_yb2s 2y ago
Yes, that can be created in principle, but you would need to modify the natural machinery (ribosome and tRNA) to make it possible.
mallomarmeasle 2y ago
Yes. Some bacteria have D-amino acids (such as D-alanine) as part of their cell walls (which otherwise contain almost entirely L-amino acids). D-amino acids are also sometimes incorporated into drugs that are synthetic peptide mimics in order to slow metabolism.
- ethbr1 2y ago
  > D-amino acids are also sometimes incorporated into drugs that are synthetic peptide mimics in order to slow metabolism. Thanks! I think that was the notecard in a dusty corner of my mind that was nagging.
- throwawaymaths 2y ago
  d-ala is not incorporated into the protein main sequence (it's part of a D-ala D-lac sugar)
frabert 2y ago
Not sure what you mean by "in a protein", but if you have a solution of some chiral chemical compound such that there's 50% of the L-enantiomer and 50% of the R-enantiomer, you get what's called a "racemic" mixture. So, yes -- mixing chirality is possible in at least one sense.
throwawaymaths 2y ago
it is possible to have mixed chirality in syntheic proteins. (see michael weiss work investigating insulin receptor binding to insulin) its basically impossible (but not totally impossible) for a living creature to be able to generate any protein with mixed chiralities. this is because a ribosome with a chamber that can support both chiralities is likely to be less efficient at protein extension. but also you need so much more trna if you want to support arbitrary d-amino acids, etc.
vixen99 2y ago
You can make these things in a lab. However Phind said "In summary, while scientists have proposed various models for how biological homochirality may have emerged, there is currently no known example of mixed protein chirality occurring in nature. Biological molecules appear to exhibit almost exclusive homochirality at the molecular level."
- ethbr1 2y ago
  It makes sense, I guess. Why would something natural want to interact with both chiralities of a target? Usually there's a reason for one... and the other is unrelated.

by ethbr1 2y ago

Basic biochemistry question (you can tell what I didn't study in uni) Is it possible to mix chirality in, say, a protein? I.e. have a portion of one chirality and another of the other?

_yb2s 2y ago

Yes, that can be created in principle, but you would need to modify the natural machinery (ribosome and tRNA) to make it possible.

mallomarmeasle 2y ago

Yes. Some bacteria have D-amino acids (such as D-alanine) as part of their cell walls (which otherwise contain almost entirely L-amino acids). D-amino acids are also sometimes incorporated into drugs that are synthetic peptide mimics in order to slow metabolism.

ethbr1 2y ago
> D-amino acids are also sometimes incorporated into drugs that are synthetic peptide mimics in order to slow metabolism. Thanks! I think that was the notecard in a dusty corner of my mind that was nagging.
throwawaymaths 2y ago
d-ala is not incorporated into the protein main sequence (it's part of a D-ala D-lac sugar)

frabert 2y ago

Not sure what you mean by "in a protein", but if you have a solution of some chiral chemical compound such that there's 50% of the L-enantiomer and 50% of the R-enantiomer, you get what's called a "racemic" mixture. So, yes -- mixing chirality is possible in at least one sense.

throwawaymaths 2y ago

it is possible to have mixed chirality in syntheic proteins. (see michael weiss work investigating insulin receptor binding to insulin) its basically impossible (but not totally impossible) for a living creature to be able to generate any protein with mixed chiralities. this is because a ribosome with a chamber that can support both chiralities is likely to be less efficient at protein extension. but also you need so much more trna if you want to support arbitrary d-amino acids, etc.

vixen99 2y ago

You can make these things in a lab. However Phind said "In summary, while scientists have proposed various models for how biological homochirality may have emerged, there is currently no known example of mixed protein chirality occurring in nature. Biological molecules appear to exhibit almost exclusive homochirality at the molecular level."

ethbr1 2y ago
It makes sense, I guess. Why would something natural want to interact with both chiralities of a target? Usually there's a reason for one... and the other is unrelated.