[Todos] Seminario INQUIMAE / DQIAQF - Martes 23 de noviembre- 13 hs.

[Gabriel Gordillo]

Seminarios DQIAQF - INQUIMAE,  Martes 23 de noviembre de 2010 - 13 hs.
 
Aula de Seminarios INQUIMAE - DQIAQF
Facultad de Ciencias Exactas y Naturales
Ciudad Universitaria - Pab. 2  -  Piso 3

The Nitrophorins from a New World Blood-Sucking Insect: NMR Spectra and Effects of Protein Side Chains on the Redox Stability of the Fe-NO Complexes 

F. Ann Walker

Department of Chemistry and Biochemistry, The University of Arizona 

Tucson, AZ  85721-0041

The nitrophorins (NP) from the salivary glands of the kissing bug (Rhodnius prolixus) have been cloned, sequenced, expressed, purified and characterized by optical, EPR, NMR, FTIR and resonance Raman spectroscopies, X-ray crystallography, and electrochemistry. These are unique heme proteins which are stabilized in the Fe(III) oxidation state, which thus insures that NO can dissociate from the proteins upon the insect's injection of them into the tissues of the victim. This injection dilutes the NO-binding proteins by approximately 100-fold. There are at least seven nitrophorins in the R. prolixus saliva that display interesting similarities and differences. All have molecular weights of about 20 kD. In this seminar the NMR spectra of high- and low-spin forms of the four nitrophorins of the adult insect will be discussed briefly to illustrate the information that can be obtained from paramagnetic heme proteins. In addition, the factors which stabilize the ferriheme-NO complexes over the corresponding ferroheme-NO complexes, and the reasons why it is fortunate that the proteins are stabilized in the Fe(III) state, will be discussed.

Background information:

"Reversible Binding of Nitric Oxide by a Salivary Nitrosylheme Protein from the Blood Sucking Insect, Rhodnius prolixus," Ribeiro, J. M. C.; Hazzard, J. M. H.; Nussenzveig, R.; Champagne, D.; Walker, F. A. Science 1993, 260, 539-541.

"Crystal Structures of a Nitric Oxide Transport Protein from a Blood-Sucking Insect," Weichsel, A.; Andersen, J. F.; Champagne, D. E.; Walker, F. A.; Montfort, W. R. Nature Struct. Biol. 1998, 5, 304-309.

"Nitric Oxide Binding to Nitrophorin 4 Induces Complete Distal Pocket Burial," Weichsel, A.; Andersen, J. F.; Roberts, S. A.; Montfort, W. R. Nature Struct. Biol. 2000, 7, 551-556.

"Kinetics and Equilibria in Ligand Binding by Nitrophorins 1-4:  Evidence for Stabilization of a NO-Ferriheme Complex through a Ligand-Induced Conformational Trap," Andersen, J. F.; Ding, X. D.; Balfour, C.; Champagne, D. E.; Walker, F. A.; Montfort, W. R. Biochemistry 2000, 39, 10118-10131.

"Ligand-Induced Heme Ruffling and Bent NO Geometry in Ultra-High Resolution Structures of Nitrophorin 4," Roberts, S. A.; Weichsel, A.; Qin, Y.; Shelnutt, J. A.; Walker, F. A.; Montfort, W. R. Biochemistry 2001, 40, 11327-11337.

"Electrochemical and NMR Spectroscopic Studies of Distal Pocket Mutants of Nitrophorin 2:  Stability, Structure and Dynamics of Axial Ligand Complexes," Shokhireva, T. Kh.; Berry, R. E.; Uno, E.; Balfour, C. A.; Zhang, H.; Walker, F. A. Proc. Natl. Acad. Sci. USA 2003, 100, 3778-3783.

"Nitric Oxide Interaction with Insect Nitrophorins, and Thoughts on the Electron Configuration of the {FeNO}6 Complex," Walker, F. A. J. Inorg. Biochem. 2005, 99, 216-236.

"Effect of the N-Terminus on Heme Cavity Structure, Ligand Equilibrium and Rate Constants, and Reduction Potentials of Nitrophorin 2 from Rhodnius prolixus," Berry, R. E.; Shokhireva, T. Kh.; Filippov, I.; Shokhirev, M. N.; Zhang, H.; Walker, F. A. Biochemistry 2007, 46, 6830-6843. 

"Assignment of the Ferriheme Resonances for Low-Spin Complexes of Nitrophorins 1 and 4 by 1H and 13C NMR Spectroscopy: Comparison to Structural Data Obtained from X-Ray Crystallography," Shokhireva, T. Kh.; Weichsel, A.; Smith, K. M.; Berry, R. E.; Shokhirev, N. V.; Balfour, C.; Zhang, H.; Montfort, W. R.; Walker, F. A. Inorg. Chem. 2007, 46, 2041-2056.

"Assignment of Ferriheme Resonances for High- and Low-Spin Forms of the Symmetrical Hemin-Reconsti-tuted Nitrophorins 1-4 by 1H and 13C NMR Spectroscopy: The Dynamics of Heme Ruffling Deformations," Sho-khireva, T. K.; Shokhirev, N. V.; Berry, R. E.; Zhang, H.; Walker, F. A. J. Biol. Inorg. Chem. 2008,13, 941-959.

"The Effect of Mutation of Carboxylate Side-Chain Amino Acids Near the Heme on the Reduction Potentials and Ligand Binding Constants of Nitrophorin 2 and its NO, Histamine and Imidazole Complexes," Berry, R. E.; Shokhirev, M. N.; Ho, A. Y. W.; Yang, F.; Shokhireva, T. K.; Zhang, H.; Weichsel, A.; Montfort, W. R.; Walker, F. A. J. Am. Chem. Soc. 2009, 131, 2313-2327.
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