Compositions and methods for solubilizing membrane proteins without the use of detergent
Disclosed are compositions and methods for isolating proteins from lipids. The isolation methods may utilize derivatives of apolipoprotein A1 for isolating membrane proteins from membranes without the use of detergent.
1. A polypeptide comprising multiple repeats of the full-length amino acid sequence of SEQ ID NO:1 as represented by the formula: (SEQ ID NO:1) n , wherein n is 3-6.
2. The polypeptide of claim 1 , wherein n is 3.
3. The polypeptide of claim 1 , wherein n is 4.
4. The polypeptide of claim 1 , wherein n is 5.
5. The polypeptide of claim 1 , wherein n is 6.
6. The polypeptide of claim 1 , as represented by the formula: N ter -(SEQ ID NO:1) n , wherein N ter is an amino acid sequence comprising a stretch of at least six histidine residues.
7. The polypeptide of claim 6 , wherein N ter further comprises a protease recognition sequence that is positioned C-terminal to the stretch of histidine residues.
8. The polypeptide of claim 1 , comprising SEQ ID NO:3.
9. A polypeptide comprising multiple repeats of a lipoprotein (LP) amino acid sequence as represented by the formula: (LP) n , wherein n is 3-6 and LP is an amino acid sequence having at least about 95% sequence identity to the full-length amino acid sequence of SEQ ID NO:1 and the polypeptide forms a holo-form nanodisc.
10. The polypeptide of claim 9 , wherein n is 4.
11. The polypeptide of claim 9 , wherein n is 5.
12. A method comprising:
(a) reacting a mixture comprising:
(1) a membrane protein present in a membrane; and
(2) the polypeptide of claim 1 ; and
(b) isolating the membrane protein from the membrane.
13. The method of claim 12 , wherein the mixture does not comprise detergent.
14. The method of claim 12 , wherein the mixture does not comprise a nonionic detergent.
15. The method of claim 12 , wherein the membrane comprises phospholipids.
16. The method of claim 12 , wherein the membrane is a phospholipid bilayer.