This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tully, R E Articles by Keister, D L Search for Related Content PubMed PubMed Citation Articles by Tully, R E Articles by Keister, D L

 Previous Article  |  Next Article 

J Bacteriol. 1991 December; 173(24): 7887-7895

research-article

Characterization of cytochromes c550 and c555 from Bradyrhizobium japonicum: cloning, mutagenesis, and sequencing of the c555 gene (cycC).

R E Tully, M J Sadowsky and D L Keister

Soybean and Alfalfa Research Laboratory, U.S. Department of Agriculture, Beltsville, Maryland 20705.

ABSTRACT

The major soluble c-type cytochromes in cultured cells of Bradyrhizobium japonicum USDA 110 comprised a CO-reactive c555 (Mr, approximately 15,500) and a non-CO-reactive c550 (Mr, approximately 12,500). Levels of cytochrome per gram of soluble protein in aerobic, anaerobic, and symbiotic cells were 32, 21, and 30 nmol, respectively, for c555 and 31, 44, and 65 nmol, respectively, for c550. The midpoint redox potentials (Em,7) of the purified cytochromes were +236 mV for c555 and +277 mV for c550. The CO reactivity of c555 was pH dependent, with maximal reactivity at pH 10 or greater. Rabbit antiserum was produced against purified c555 and used to screen a B. japonicum USDA 110 genomic DNA expression library in lambda gt11 for a downstream portion of the c555 gene (cycC). This sequence was then used to probe a cosmid library for the entire c555 locus. The nucleotide sequence shows an open reading frame of 149 amino acids, with an apparent signal sequence at the N terminus and a heme-binding site near the C terminus. The deduced amino acid sequence is similar to those of the cytochromes c556 of Rhodopseudomonas palustris and Agrobacterium tumefaciens. The cycC gene was mutagenized by insertion of a kanamycin resistance cassette and homologously recombined into the B. japonicum genome. The resulting mutant made no c555 but made normal amounts of c550. The levels of membrane cytochromes were unaffected. The mutant and wild type exhibited identical phenotypes when used to nodulate plants of soybean (Glycine max L. Merr.), with no significant differences in nodule number, nodule mass, or total amount of N2 fixed.

---

J Bacteriol. 1991 December; 173(24): 7887-7895

This article has been cited by other articles:

• Mesa, S., Hauser, F., Friberg, M., Malaguti, E., Fischer, H.-M., Hennecke, H. (2008). Comprehensive Assessment of the Regulons Controlled by the FixLJ-FixK2-FixK1 Cascade in Bradyrhizobium japonicum. J. Bacteriol. 190: 6568-6579 [Abstract] [Full Text]