'''Crystal structure of ferrous cimex nitrophorin'''
===Crystal structure of ferrous cimex nitrophorin===
==Overview==
Certain bloodsucking insects deliver nitric oxide (NO) while feeding, to induce vasodilation and inhibit blood coagulation. We have expressed, characterized, and determined the crystal structure of the Cimex lectularius (bedbug) nitrophorin, the protein responsible for NO storage and delivery, to understand how the insect successfully handles this reactive molecule. Surprisingly, NO binds not only to the ferric nitrophorin heme, but it can also be stored as an S-nitroso (SNO) conjugate of the proximal heme cysteine (Cys-60) when present at higher concentrations. EPR- and UV-visible spectroscopies, and a crystallographic structure determination to 1.75-A resolution, reveal SNO formation to proceed with reduction of the heme iron, yielding an Fe-NO complex. Stopped-flow kinetic measurements indicate that an ordered reaction mechanism takes place: initial NO binding occurs at the ferric heme and is followed by heme reduction, Cys-60 release from the heme iron, and SNO formation. Release of NO occurs through a reversal of these steps. These data provide, to our knowledge, the first view of reversible metal-assisted SNO formation in a protein and suggest a mechanism for its role in NO release from ferrous heme. This mechanism and Cimex nitrophorin structure are completely unlike those of the nitrophorins from Rhodnius prolixus, where NO protection is provided by a large conformational change that buries the heme nitrosyl complex, highlighting the remarkable evolution of proteins that assist insects in bloodfeeding.
==About this Structure==
==About this Structure==
2IMQ is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Cimex_lectularius Cimex lectularius]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2IMQ OCA].
2IMQ is a 1 chain structure of sequence from [http://en.wikipedia.org/wiki/Cimex_lectularius Cimex lectularius]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2IMQ OCA].
==Reference==
==Reference==
Heme-assisted S-nitrosation of a proximal thiolate in a nitric oxide transport protein., Weichsel A, Maes EM, Andersen JF, Valenzuela JG, Shokhireva TKh, Walker FA, Montfort WR, Proc Natl Acad Sci U S A. 2005 Jan 18;102(3):594-9. Epub 2005 Jan 6. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/15637157 15637157]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 07:40:01 2008''
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Feb 17 04:11:59 2009''
Revision as of 02:11, 17 February 2009
This article has been automatically seeded. Changes to this page should pertain to the PDB entry only and not to the protein or biomolecule in general.
2IMQ is a 1 chain structure of sequence from Cimex lectularius. Full crystallographic information is available from OCA.
Reference
Weichsel A, Maes EM, Andersen JF, Valenzuela JG, Shokhireva TKh, Walker FA, Montfort WR. Heme-assisted S-nitrosation of a proximal thiolate in a nitric oxide transport protein. Proc Natl Acad Sci U S A. 2005 Jan 18;102(3):594-9. Epub 2005 Jan 6. PMID:15637157
