[redskytonight820]

Does anyone know what kinds of forces or bonds anchor an integral membrane protein in a biological membrane?

From my undergrad gen bio 2, i believe it's due to ionic interactions between residiues of positive side chains and negatively charged hydrophobic heads. Am I right? Are there more?

I'm not too sure about peripheral membrane proteins though.. those are tricky... what forces hold a peripheral membrane protein to the membrane?

and also if integral membrane proteins and peripheral membrane proteins are present with each other, what could be done to solubilize each of the two types of membrane proteins?

[Yggdrasil]

Integral membrane proteins are held in the membrane by hydrophobic regions (usually alpha helices, but they can also be lipid molecules attached to the protein post-translationally).  that are soluble in the interior of the lipid bilayer but not in the aqueous environment of the cytoplasm.

Peripheral membrane proteins are brought to the membrane through electrostatic interactions with the headgroups of specific phospholipids (phosphoinositides commonly recruit peripheral membrane proteins) or through interactions with integral membrane proteins.

Given this information, can you think of a way to separate integral membrane proteins from peripheral membrane proteins?

[redskytonight820]

Thank you

I see now, with the info, how easy it is to separate these.

Integral proteins = hydrophobic
Peripheral proteins = hydrophillic

Voilla! And to solubilize each would just to put the integral proteins in ehter and peripheral proteins in water.

Are there any other interactions or forces taht hold these proteins in their respective places in the membrane?

[Rabn]

I'm curious where the question originates from. If I wanted to solubilize the peripheral proteins I would change the ionic strength of the aqueous environment, increase it to break up the interaction with the membrane.

[Yggdrasil]

Thank you

I see now, with the info, how easy it is to separate these.

Integral proteins = hydrophobic
Peripheral proteins = hydrophillic

Voilla! And to solubilize each would just to put the integral proteins in ehter and peripheral proteins in water.

Are there any other interactions or forces taht hold these proteins in their respective places in the membrane?

Unfortunately, all proteins have hydrophobic regions.  In soluble proteins, these hydrophobic regions form the core of the protein (in fact, the exclusion of these hydrophobic residues from the surface of the protein is a major driving force in protein folding).  So, if you put proteins in ether, they will literally turn inside out and have their hydrophobic cores on the outside and their hydrophilic cores on the inside.

Rabn's answer is the one most commonly used by biologists.  Peripheral membrane proteins are associated with the membrane lipids/integral membrane proteins through noncovalent, electrostatic interactions.  By washing cell membranes with a high salt solution (typically ~1M NaCl), one can dissociate the peripheral membrane proteins from the membrane so that they are now in the solution.  Because integral membrane proteins are stably associated with membrane through the hydrophobic effect, they will not dissociate from membranes upon a high salt wash and will remain in the membrane extract (which can be separated from the rest of the solution by centrifugation).