 |
PDBsum entry 1cxy
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Electron transport
|
PDB id
|
|
|
|
1cxy
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
|
|
* Residue conservation analysis
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Structure and characterization of ectothiorhodospira vacuolata cytochrome b(558), A prokaryotic homologue of cytochrome b(5).
|
|
|
Authors
|
|
V.Kostanjevecki,
D.Leys,
G.Van driessche,
T.E.Meyer,
M.A.Cusanovich,
U.Fischer,
Y.Guisez,
J.Van beeumen.
|
|
|
Ref.
|
|
J Biol Chem, 1999,
274,
35614-35620.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
A soluble cytochrome b(558) from the purple phototropic bacterium
Ectothiorhodospira vacuolata was completely sequenced by a combination of
automated Edman degradation and mass spectrometry. The protein, with a measured
mass of 10,094.7 Da, contains 90 residues and binds a single protoheme.
Unexpectedly, the sequence shows homology to eukaryotic cytochromes b(5). As no
prokaryotic homologue had been reported so far, we developed a protocol for the
expression, purification, and crystallization of recombinant cytochrome b(558).
The structure was solved by molecular replacement to a resolution of 1.65 A. It
shows that cytochrome b(558) is indeed the first bacterial cytochrome b(5) to be
characterized and differs from its eukaryotic counterparts by the presence of a
disulfide bridge and a four-residue insertion in front of the sixth ligand
(histidine). Eukaryotes contain a variety of b(5) homologues, including soluble
and membrane-bound multifunctional proteins as well as multidomain enzymes such
as sulfite oxidase, fatty-acid desaturase, nitrate reductase, and lactate
dehydrogenase. A search of the Mycobacterium tuberculosis genome showed that a
previously unidentified gene encodes a fatty-acid desaturase with an N-terminal
b(5) domain. Thus, it may provide another example of a bacterial b(5) homologue.
|
|
|
|
|
|
|
|
Figure 4.
Fig. 4. Detail of the weighted 2F[o]  F[c]
electron density map surrounding the heme group and both heme
ligands with the final model superposed.
|
|
Figure 8.
Fig. 8. Comparison of the electrostatic molecular
surfaces around the heme pockets of cytochromes b[558] (A) and
b[5] (B). The surface is colored according to the electrostatic
potential (red, negative; blue, positive) and made transparent;
the heme group is blue. This figure was generated by GRASP (41).
|
|
|
|
|
|
The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(1999,
274,
35614-35620)
copyright 1999.
|
|
|
|
|
|
|
