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

[andrea en qi.fcen.uba.ar]

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.