1cxy

Publication Abstract from PubMed

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.

Structure and characterization of Ectothiorhodospira vacuolata cytochrome b(558), a prokaryotic homologue of cytochrome b(5).,Kostanjevecki V, Leys D, Van Driessche G, Meyer TE, Cusanovich MA, Fischer U, Guisez Y, Van Beeumen J J Biol Chem. 1999 Dec 10;274(50):35614-20. PMID:10585439^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.