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How are miniproteins any different than just peptides? The article references "miniproteins"as being the same as "minipetides"... as though these are both diff

How are miniproteins any different than just peptides? The article references "miniproteins"as being the same as "minipetides"... as though these are both different from regular peptides. Wikipedia states that peptides are "approximately 50 or fewer amino acids" [0] while minipeptides are "a length of less than 100-150 amino acids" [1]. Is this article really just saying that "peptides are upending cell biology"? [0] https://en.wikipedia.org/wiki/Peptide https://en.wikipedia.org/wiki/Peptide [1] https://en.wikipedia.org/wiki/Micropeptide https://en.wikipedia.org/wiki/Micropeptide

hirenj 7y ago
The difference is that the peptides are generated by chopping up larger proteins, while miniproteins are synthesised as short proteins. I.e. you need other enzymes to turn a protein into peptide, but a microprotein only needs to be translated to be short!
doctoboggan 7y ago
From the article: > OTHER SHORT AMINO ACID chains, often called peptides or polypeptides, abound in cells, but they are pared-down remnants of bigger predecessors. Myoregulin and its diminutive brethren, in contrast, are born small.
- gilleain 7y ago
  Thats a bit confusing, as proteins _are_ polypeptides. All proteins are (poly)peptides, but not all peptides are proteins.
gilleain 7y ago
The boundary between 'peptide' and 'protein' is a little fuzzy. There are 'small proteins' like: https://en.m.wikipedia.org/wiki/Thionin https://en.m.wikipedia.org/wiki/Thionin that are 45-48 amino acids which is less than the (arbitrary) lower limit of 50. One distinguishing feature of a protein is that it folds, while peptides usually are too short to have a defined fold.
- glenvdb 7y ago
  > while peptides usually are too short to have a defined fold. That's not strictly true. My PhD project has looked at an entire class of peptides that are known to fold in to alpha-helices when bound to a cell membrane e.g. https://www.rcsb.org/structure/2k9b https://www.rcsb.org/structure/2k9b. There are many others that are known to fold into beta-sheets too.
  - gilleain 7y ago
    Fair, but I would not really call a single helix a 'fold', either! Ok, so I'm playing with definitions here a bit. Clearly 2k9b adopts a helical structure so it is 'folded' in some sense. However it has no tertiary structure. Structural proteins like collagen are different again. They have a simple fold that could be described as quaternary (multichain), although that is again an abuse of terminology. There are also some small proteins (peptides?) held together by disulphide links that have no secondary strucure to speak of. I think these are Class 4 in CATH, but I do not remember. What is an example of a beta-sheet peptide? Amyloid is beta, I thought, but sheets are not normally stable outside sandwiches, barrels, etc
    - flobosg 7y ago
      > What is an example of a beta-sheet peptide? WW domains[1] fold stably into a three-stranded sheet. Also, not strictly a sheet, but beta hairpin motifs (e.g. tryptophan zippers[2]) are known to be stable isolated from their parental domains. [1]: http://www.rcsb.org/structure/5VTJ http://www.rcsb.org/structure/5VTJ [2]: http://www.rcsb.org/structure/1LE0 http://www.rcsb.org/structure/1LE0

hirenj 7y ago

The difference is that the peptides are generated by chopping up larger proteins, while miniproteins are synthesised as short proteins. I.e. you need other enzymes to turn a protein into peptide, but a microprotein only needs to be translated to be short!

doctoboggan 7y ago

From the article: > OTHER SHORT AMINO ACID chains, often called peptides or polypeptides, abound in cells, but they are pared-down remnants of bigger predecessors. Myoregulin and its diminutive brethren, in contrast, are born small.

gilleain 7y ago
Thats a bit confusing, as proteins _are_ polypeptides. All proteins are (poly)peptides, but not all peptides are proteins.

gilleain 7y ago

The boundary between 'peptide' and 'protein' is a little fuzzy. There are 'small proteins' like: https://en.m.wikipedia.org/wiki/Thionin https://en.m.wikipedia.org/wiki/Thionin that are 45-48 amino acids which is less than the (arbitrary) lower limit of 50. One distinguishing feature of a protein is that it folds, while peptides usually are too short to have a defined fold.

glenvdb 7y ago
> while peptides usually are too short to have a defined fold. That's not strictly true. My PhD project has looked at an entire class of peptides that are known to fold in to alpha-helices when bound to a cell membrane e.g. https://www.rcsb.org/structure/2k9b https://www.rcsb.org/structure/2k9b. There are many others that are known to fold into beta-sheets too.
- gilleain 7y ago
  Fair, but I would not really call a single helix a 'fold', either! Ok, so I'm playing with definitions here a bit. Clearly 2k9b adopts a helical structure so it is 'folded' in some sense. However it has no tertiary structure. Structural proteins like collagen are different again. They have a simple fold that could be described as quaternary (multichain), although that is again an abuse of terminology. There are also some small proteins (peptides?) held together by disulphide links that have no secondary strucure to speak of. I think these are Class 4 in CATH, but I do not remember. What is an example of a beta-sheet peptide? Amyloid is beta, I thought, but sheets are not normally stable outside sandwiches, barrels, etc
  - flobosg 7y ago
    > What is an example of a beta-sheet peptide? WW domains[1] fold stably into a three-stranded sheet. Also, not strictly a sheet, but beta hairpin motifs (e.g. tryptophan zippers[2]) are known to be stable isolated from their parental domains. [1]: http://www.rcsb.org/structure/5VTJ http://www.rcsb.org/structure/5VTJ [2]: http://www.rcsb.org/structure/1LE0 http://www.rcsb.org/structure/1LE0