Expression, purification, and solid-state NMR characterization of the membrane binding heme protein nitrophorin 7 in two electronic spin states.

The nitrophorins (NPs) comprise a group of NO transporting ferriheme b proteins found in the saliva of the blood sucking insect Rhodnius prolixus . In contrast to other nitrophorins (NP1-4), the recently identified membrane binding isoform NP7 tends to form oligomers and precipitates at higher concentrations in solution. Hence, solid-state NMR (ssNMR) was employed as an alternative method to gain structural insights on the precipitated protein.