Why so few beta-sheet membrane proteins?

[poobear]

Hi all

Why are there so few membrane proteins with beta-sheets? 99% seems to be alfa-helices

And the few few that exists, why are they only very complicated beta-barrels? Why not like transmembrane alfa-helices but with beta-sheets

/Thanks

[JackBean]

Let's start from the end.
The alpha-helices are hold together by H-bonding between consequent amino acids, whereas for beta-sheets you need several beta-strands, which make H-bonds in between each other
So, you can have only one helix (not only transmembrane), but you can't have only one beta-strand.

Regarding the first question, look for how many amino acids you need to pass through the membrane for helix and how many for beta-strand

[MrMistery]

jack, I think your answer to the former question is wrong, since a beta sheet actually uses less amino acids to cross a membrane than an alpha helix. I think the reason there's more alpha helical proteins is the higher hydrophobicity of the alpha helix compared to the beta sheet

[zami'87.]

As I remember alpha helices slide past others and they're more convenient for signal transduction or transport...beta barrels are rigid structures...