transmembrane AA's

[boardsbandit524]

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I have found several conflicting sources on this, what AA's are found in transmembrane domains?

Obviously the normal non polars (GLY ALA VAL LEU ILE PRO)

here is where it gets weird

also the aromatics? (PHE TRP but TYRO? (looks polar))
also the sulfurs? (MET but CYS? (looks polar))

Just a little confused any help would be appreciated...

 

[dilated]

There's two types of polarity for AAs, the polarity type like tyrosine and the ionic type like aspartate. For transmembrane purposes having a charge at physiologic pH puts you out of the running. Being polar is kind of a gray area (I wouldn't expect to see many TYR or CYS in a transmembrane domain), but for these questions there's usually only 1 choice with no charged amino acids.

 

[westernmed007]

had one with a CYS in the correct answer... (from a legit q source too)

 

[Mediculous]

I wouldn't expect cysteine to be in a transmembrane domain, since it's hydrophilic, but I would guess that 2 cysteines bonding with a disulfide bridge to form cystine could be found in the transmembrane region. Does that sound right?

 

[westernmed007]

Nope: its ILE PHE VAL LEU ILE TRP CYS LEU in the answer choice....

i guess i assume that it finds another and bonds it...

 

[DwyaneWade]

I have found several conflicting sources on this, what AA's are found in transmembrane domains?

Obviously the normal non polars (GLY ALA VAL LEU ILE PRO)

here is where it gets weird

also the aromatics? (PHE TRP but TYRO? (looks polar))
also the sulfurs? (MET but CYS? (looks polar))

Just a little confused any help would be appreciated...

That question was on world right? The key was that none of the other answer choices were good.

Also tyrosine has that huge aromatic ring, so its still pretty nonpolar. Cysteine has a sulfur atom, check out the electronegativity of sulfur, not much polarity there.