2XLM: Cytochrome C Prime From Alcaligenes Xylosoxidans: Ferrous Recombinant Native With Bound No

Citation:
Abstract
Hemoproteins play central roles in the formation and utilization of nitric oxide (NO) in cellular signaling, as well as in protection against nitrosative stress. Key to heme-nitrosyl function and reactivity is the Fe coordination number (5 or 6). For (five-coordinate) 5c-NO complexes, the potential for NO to bind on either heme face exists, as in the microbial cytochrome c' from Alcaligenes xylosoxidans (AxCYTcp), which forms a stable proximal 5c-NO complex via a distal six-coordinate NO intermediate and a putative dinitrosyl species. Strong parallels between the NO-binding kinetics of AxCYTcp, the eukaryotic NO sensor soluble guanylate cyclase, and the ferrocytochrome c/cardiolipin complex have led to the suggestion that a distal-to-proximal NO switch could contribute to the selective ligand responses in gas-sensing hemoproteins. The proximal NO-binding site in AxCYTcp is close to a conserved basic (Arg124) residue that is postulated to modulate NO reactivity. We have replaced Arg124 by five different amino acids and have determined high-resolution (1.07-1.40 A) crystallographic structures with and without NO. These, together with kinetic and resonance Raman data, provide new insights into the mechanism of distal-to-proximal heme-NO conversion, including the determinants of Fe-His bond scission. The Arg124Ala variant allowed us to determine the structure of an analog of the previously unobserved key 5c-NO distal intermediate species. The very high resolution structures combined with the extensive spectroscopic and kinetic data have allowed us to provide a fresh insight into heme reactivity towards NO, a reaction that is of wide importance in biology.
PDB ID: 2XLMDownload
MMDB ID: 86027
PDB Deposition Date: 2010/7/21
Updated in MMDB: 2010/11
Experimental Method:
x-ray diffraction
Resolution: 1.19  Å
Source Organism:
Similar Structures:
Biological Unit for 2XLM: dimeric; determined by author and by software (PISA)
Molecular Components in 2XLM
Label Count Molecule
Proteins (2 molecules)
2
Cytochrome C'
Molecule annotation
Chemicals (6 molecules)
1
2
2
2
3
2
* Click molecule labels to explore molecular sequence information.

Citing MMDB
.