Nitrophorins are nitric oxide transporting proteins utilized by the blood sucking insect Rhodnius prolixus. What’s unique about these proteins, is they work in tandem with histamines to not only mask their feeding, but also utilize the unique biological characteristic that nitric oxide possesses at low concentrations, by delivering the compound directly to the bite site. This is done by the protein’s sensitivity to pH differences in both the insect saliva and the host’s bloodstream. Which is a unique mechanism for this protein. The kinetics show that the mechanism is biphasic, meaning that there is a fast phase and a slow phase within the delivery system. This leads to the chemistry of the pH sensitivity, and how the protein responds accordingly to the pH changes. This series of four proteins facilitates the blood meal for easy feeding.

References:

Ding, X. D. (1999). Nitric Oxide Binding to the Ferri- and Ferroheme States of Nitrophorin 1, a Reversible NO-Binding Heme Protein from the Saliva of the Blood-Sucking Insect, Rhodnius prolixus. Journal of American Chemical Society, 128-138.