[jyounker]

> What you have to be careful about here is that the structure that were available 30 years ago were quite strongly biased by what was experimentally tractable.... ie the recurrence of the same folds is in part related to what crystallised well.

It was biased in some sense towards those things that could be crystalized, but but at that time we were already seeing the same sorts of recurring motifs with cryo-em which is much less restrictive in the required preparations. (Purify it and flash freeze it.)

In the last 30 years there's nothing that has overturned the recurrence of motifs in protein structure. It's just become more and more established.

This paper confirms that.

The methods they're using are interesting, but the fundamental result isn't surprising.

[DrScientist]

No one is arguing reuse is a surprise - there used to be a joke in the early days of protein fold prediction - that if the protein amino acid sequence was a certain length - you just predict TIM barrel and you'd be right.

the question is a separate one - how much of protein universe of folds have already been seen?

[jyounker]

So we're in agreement. The expectation is that biochemistry here on Earth only produces a small proportion of the possible structures.