Nitrophorins Rhodnius prolixus

C. Early Work on the Nitrophorins from Rhodnius prolixus... 

Fig. 1. Nitric oxide (NO) synthesis by nitric oxide synthase (NOS) (upper left), NO reaction with soluble guanylate cyclase (sGC) (middle), and formation of cyclic GMP, which causes tissue-specific signaling (right). The roles of the salivary nitrophorins from Rhodnius prolixus in storing and releasing NO and binding histamine are included (lower left).

Fig. 23. The dissociation constants and redox stability of the NO and histamine complexes of the nitrophorins from the saliva of Rhodnius prolixus, and how they aid the insect in obtaining a sufficient blood meal. Modified from Ref (.31).

Montfort, W. R. Weichsel, A. Andersen, J. F. Nitrophorins and Related Antihemostatic Lipocahns from Rhodnius prolixus and Other Blood-Sucking Arthropods. Biochim. Biophys. Acta. 2000, in press. 

Since the primary structure of a peptide determines the global fold of any protein, the amino acid sequence of a heme protein not only provides the ligands, but also establishes the heme environmental factors such as solvent and ion accessibility and local dielectric. The prevalent secondary structure element found in heme protein architectures is the a-helix however, it should be noted that p-sheet heme proteins are also known, such as the nitrophorin from Rhodnius prolixus (71) and flavocytochrome cellobiose dehydrogenase from Phanerochaete chrys-osporium (72). However, for the purpose of this review, we focus on the structures of cytochromes 6562 (73) and c (74) shown in Fig. 2, which are four-a-helix bundle protein architectures and lend themselves as resource structures for the development of de novo designs. 

The nitrophorins of the kissing bug, Rhodnius prolixus, are unique NO-binding heme proteins, in that they are stable as Fe heme centers and are not autoreduced by excess NO in the solution as are other heme proteins such as met-myoglobin consistent with this property, their reduction potentials are about 300 mV more negative than that of met-myoglobin (E° 0 mV vs. SHE at pH = 7.5) is... 

In a different organism, the effect of pH on NO bound to a heme group in the protein nitrophorin 1 helps the bloodsucking insect Rhodnius prolixus obtain a meal. ... 

The NO-binding Nitrophorin 1 (NP1), from the saliva of the blood-sucking insect Rhodnius prolixus, contains two diamagnetic FeNO 6 ferrihemes, with i/NO at 1,904 cm-1 and 1,917 cm-1. They exist in a pH-dependent ratio and bind NO reversibly without being reduced. Alternative electronic distribution assignments as FemNO or FenNO+ rely on IR, EPR, NMR, FTIR, and... 

Nitrophorins are haem proteins which are present in the salivary glands of the blood-sucking insect Rhodnius prolixus. Binding of NO to the Fe(III) centre in nitrophorin (NPl) is reversible, and is dependent on pH. Crucial to the process of blood-sucking by Rhodnius prolixus is the fact that NO binds 10 times more tightly at pH 5 (i.e. the pH of the saliva... 

Ribeiro JM, Schneider M, Guimaraes JA. Purification and characterization of prolixin S (nitrophorin 2), the salivary anticoagulant of the blood-sucking bug rhodnius prolixus. Biochem J 1995 308(Pt l) 243-249. 

The structure above (determined by X-ray diffraction, PDB code 20FR) is that of a nitrophorin from Rhodnius prolixus complexed with NO at pH 5.6. The haem unit is bound... 

Maes, E.M., Walker, F.A., Montfort, W.R., Czemuszewicz, R.S. Resonance Raman spectroscopic study of nitrophorin 1, a nitric oxide-binding heme protein from Rhodnius prolixus, and its nitrosyl and cyano adducts. J. Am. Chem. Soc. 123, 11664-11672 (2001)... 

The nitrophorins comprise a group of, NO transporting proteins found in the saliva of the blood sucking insect Rhodnius prolixus. ssNMR vras employed as an alternative method to gain structural insights on the precipitated protein by Varghese et Using isotopically la-... 

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