Compositions and methods for the delivery of oxygen
H-NOX proteins are mutated to exhibit improved or optimal kinetic and thermodynamic properties for blood gas O 2 delivery. The engineered H-NOX proteins comprise mutations that impart altered O 2 or NO ligand-binding relative to the corresponding wild-type H-NOX domain, and are operative as physiologically compatible mammalian blood O 2 gas carriers. The invention also provides pharmaceutical compositions, kits, and methods that use wild-type or mutant H-NOX proteins for the treatment of any condition for which delivery of O 2 is beneficial.
1. An isolated H-NOX protein comprising at least one distal pocket mutation that alters the O 2 dissociation constant or NO reactivity compared to that of a corresponding wild-type H-NOX protein, wherein the O 2 dissociation constant of the mutant H-NOX protein is within 2 orders of magnitude of that of hemoglobin, wherein the NO reactivity of the mutant H-NOX protein is at least 10-fold lower than that of hemoglobin, wherein the H-NOX protein does not comprise a guanylyl cyclase catalytic domain, wherein the distal pocket mutation comprises a substitution at a residue that corresponds to at least one of Thr4, Ile5, Thr8, Trp9, Trp67, Asn74, Ile75, Phe78, Phe82, Tyr140, and Leu144 of a T. tengcongensis H-NOX of SEQ ID NO: 54, and wherein the mutant H-NOX protein is not T. tengcongensis H-NOX Y140L, T. tengcongensis H-NOX F78Y/Y140L, T. tengcongensis H-NOX W9F, T. tengcongensis H-NOX W9F/Y140L, H. sapiens β1 H-NOX (1-385) I145Y, or L. pneumophilia 2 H-NOX F142Y.
2. The isolated H-NOX protein of claim 1 , wherein the O 2 dissociation constant of the mutant H-NOX protein is between 1 nM and 1 mM at 20° C., and the NO reactivity of the mutant H-NOX protein is less than 700 s −1 at 20° C.
3. The isolated H-NOX protein of claim 1 , wherein the O 2 dissociation constant of the H-NOX protein is between 2 nM and 50 μM at 20° C.
4. The isolated H-NOX protein of claim 1 , wherein the NO reactivity of the H-NOX protein is less than 1 s −1 at 20° C.
5. The isolated H-NOX protein of claim 1 , wherein the NO reactivity of the H-NOX protein is at least 100-fold lower than that of human hemoglobin alpha.
6. The isolated H-NOX protein of claim 1 , wherein the k off for oxygen of the H-NOX protein is between 0.01 s −1 and 200 s −1 at 20° C.
7. The isolated H-NOX protein of claim 1 , wherein the rate of heme autoxidation of the H-NOX protein is less than 1 h −1 at 37° C.
8. The isolated H-NOX protein of claim 1 , wherein the distal pocket mutation is a L144F mutation.
9. The isolated H-NOX protein of claim 1 , wherein the H-NOX protein is a T. tengcongensis H-NOX protein comprising a L144F mutation in SEQ ID NO: 54.
10. The isolated H-NOX protein of claim 1 , wherein the H-NOX protein is a fusion protein that includes an H-NOX domain and part or all of another protein.
11. The isolated H-NOX protein of claim 1 , wherein the H-NOX protein is covalently bound to polyethylene glycol.
12. An isolated H-NOX protein comprising a distal pocket mutation wherein the O 2 dissociation constant of the H-NOX protein is within 2 orders of magnitude of that of hemoglobin, wherein the NO reactivity of the mutant H-NOX protein is at least 10-fold lower than that of hemoglobin, and wherein the distal pocket mutation is at an amino acid position corresponding to position L144 of T. tengcongensis H-NOX of SEQ ID NO: 54, wherein the H-NOX protein does not comprise a guanylyl cyclase catalytic domain.
13. The isolated H-NOX protein of claim 12 , wherein the H-NOX protein is a fusion protein that includes an H-NOX domain and part or all of another protein.
14. The isolated H-HOX protein of claim 12 , wherein the H-NOX protein is covalently bound to polyethylene glycol.
15. The isolated H-NOX protein of claim 13 , wherein the H-NOX protein is covalently bound to polyethylene glycol.
16. An isolated H-NOX protein comprising a distal pocket mutation, wherein the O 2 dissociation constant of the mutant H-NOX protein is within 2 orders of magnitude of that of hemoglobin, wherein the NO reactivity of the mutant H-NOX protein is at least 10-fold lower than that of hemoglobin, wherein the H-NOX protein is a T. tengcongensis H-NOX protein comprising a L144F mutation in SEQ ID NO: 54 and does not comprise a guanylyl cyclase catalytic domain, wherein the H-NOX protein is a fusion protein that includes an H-NOX domain and part or all of another protein, and wherein the H-NOX protein is covalently bound to polyethylene glycol.