Molecular Modeling: Does a proline chain fold or tangle up?

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Discussion Overview

The discussion revolves around the implications of attaching a long proline chain to the C terminal of a protein, specifically in the context of protein folding and stability when creating a fusion protein. The scope includes theoretical considerations, practical applications in protein design, and the potential effects on secondary and tertiary structures.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether attaching a long proline chain (8 or more residues) to a protein would affect its folding when connecting to another protein.
  • Another participant notes that the impact of proline on folding is highly specific to the protein's secondary and tertiary structure, suggesting that general answers are not feasible.
  • A participant mentions that proline's unique structure can lead to restrictions in conformers, potentially causing loss of secondary structure, as evidenced by past observations of mutant proteins.
  • It is proposed that using flexible linkers made of small amino acids is common practice for fusion proteins, while long proline chains may lead to rigidity and polyproline helices.
  • A later reply indicates a preference for rigidity in the design, specifying a sequence of amino acids intended for use as a linker.

Areas of Agreement / Disagreement

Participants express differing views on the effects of proline chains on protein folding, with no consensus reached on the generalizability of the effects or the best practices for linker design.

Contextual Notes

The discussion highlights the dependence on specific protein structures and the limitations of generalizing findings from one system to another. There are unresolved considerations regarding the stability and folding of proteins when modified with proline chains.

Who May Find This Useful

Researchers and practitioners involved in protein engineering, molecular biology, and those interested in the structural implications of amino acid modifications in protein design.

cimmerian
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It's probably a stupid question but is it possible to attach a long proline chain - 8 or more residues - at the C terminal of a protein and have it connect to another protein and not affect folding? It's for a project and it's not actually necessary but I have to make a protein that binds to an antigen. I want to attach that protein to another protein that let's it get picked up and disposed of. Actually, I think that would go beyond the MW limit but still...
 
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This is a very specific question which can't be answered in any general way. It really depends on the secondary and tertiary structure of the protein you are studying.

You can check out Ramachandran plots to see what Pro likes to do. I recall that the tertiary amine and ring structure put restrictions on the conformers of Pro containing peptides such that a loss of secondary structure may result. An old-timer post doc in my lab mentioned mutant proteins where some AA was mutated to a Pro and led to things like unwinding of helices and what not.

Just to reiterate though, this question is very specific to the system you are studying and no general answers can really be given. Looking at the crystal structures can give hints but nothing is fool-proof AFAIK.
 
When creating a fusion protein (concatenating two separate proteins or protein domains into a single polypeptide chain), one generally uses a flexible linker composed of small amino acids like glycine, serine, and alanine. Long proline chains tend to form polyproline helices, which would likely result in a somewhat more rigid linker. In some cases, the N- or C-termini of proteins are buried within the structure so adding a protein onto the terminus will destabilize the protein.

Here's a paper that you may find useful:
https://www.ncbi.nlm.nih.gov/pubmed/23026637

Here's another potentially useful resource:
http://partsregistry.org/Protein_domains/Linker
 
Thanks! I actually want it to be rigid so I'm going to use GSGPSPTPGSG.
 

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