Effect of mutation of carboxyl side-chain amino acids near the heme on the midpoint potentials and ligand binding constants of nitrophorin 2 and its NO, histamine, and imidazole complexes.

ABSTRACT: Nitrophorins (NPs) are a group of NO-carrying heme proteins found in the saliva of a blood-sucking insect from tropical Central and South America, Rhodnius prolixus, the "kissing bug". NO is kept stable for long periods of time by binding it as an axial ligand to a ferriheme center. The fact that the nitrophorins are stabilized as Fe(III)-NO proteins is a unique property because most heme proteins are readily autoreduced by excess NO and bind NO to the Fe(II) heme irreversibly (K(d)s in the picomolar range). In contrast, the nitrophorins, as Fe(III) heme centers, have K(d)s in the micromolar to nanomolar range and thus allow NO to dissociate upon dilution following injection into the tissues of the victim. This NO can cause vasodilation and thereby allow more blood to be transported to the

SUBMITTER: Berry RE 

PROVIDER: S-EPMC2647857 | biostudies-literature | 2009 Feb

REPOSITORIES: biostudies-literature