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

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)
Cytochrome C'
Molecule annotation
Chemicals (6 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB