Talk:Protein homology

Structural vs. functional homology

There's a redirect from structural homology, protein to here, and I've got a feeling this is a misunderstanding! - that the two need to be differentiated! (Disambiguation page?)

My impression is that proteins are properly described as homologous if their structure and function(s) correspond/match/overlap, importantly, in a way that suggests/confirms that they share a common evolutionary origin . . and they'll be described as structurally homologous to point out similarity of structure alone.

Structural homology may be mentioned simply without opinion/commitment on (a) whether the proteins' functions correspond, and/or (b) whether the proteins have a shared origin. In other contexts there may be the thought that they don't, and at the extreme a writer may be saying that the agreement in structure is noteworthy because the proteins are not homologous in function and/or origin.

If I'm right the redirect is wrong and needs reversing.

The complication is if some writers sometimes use homologous when they mean only structurally homologous (ie "for short"). If this does happen, enough to matter, a disambiguation page is needed.

These are my impressions. Does anyone actually know? - please edit the article / undo the redirect and make a stub, as appropriate!

SquisherDa (talk) 14:17, 5 February 2012 (UTC)

I'm inclined to agree with the need for expansion/clarification, as it is right now it doesn't seem like we have an article that adequately explains structural and/or functional protein homology. I can link this discussion from WT:MCB, might help attract some more attention. (+)H₃N-Protein\Chemist-CO₂(-) 16:22, 6 February 2012 (UTC)

Interesting discussion. Functional homology is often a result of structural homology that in turn results from sequence homology that suggests (but is not proof of) a common ancestor. There are of course notable exceptions that are a result of convergent or divergent evolution. Sequence similarity alone is enough to suggest a common ancestor. The case becomes stronger if structure is also conserved and even stronger if function is conserved. The link between sequence and structure is probably stronger than between structure and function. Hence two proteins with different functions are likely to be homologous if they are sufficiently similar in sequence and in structure. Therefore I think the redirect from structural homology to this article is probably OK but I agree that this article needs expansion. Boghog (talk) 19:45, 20 February 2012 (UTC)

The point of Reeck et al. (PMID 3621342) is that similarity ≠ homology. Furthermore anything that is homologous is by definition derived from a common ancestor. Boghog (talk) 20:14, 20 February 2012 (UTC)