The Bradyrhizobium japonicum fegA gene encodes an iron-regulated outer membrane protein with similarity to hydroxamate-type siderophore receptors.

摘要: Iron is important in the symbiosis between soybean and its nitrogen-fixing endosymbiont Bradyrhizobium japonicum, yet little known about rhizobial iron acquisition strategies. Analysis of outer membrane proteins (OMPs) from B. japonicum 61A152 identified three iron-regulated OMPs size range several receptors for Fe(III)-scavenging siderophores. One proteins, FegA, was purified microsequenced, a reverse genetics approach used to clone fegA-containing DNA fragment. Sequencing this fragment revealed single open reading frame 750 amino acids. A putative N-terminal signal sequence 14 acids which would result mature protein 736 with molecular mass 80,851 Da predicted. FegA shares significant acid similarity Fe(III)-siderophore gram-negative bacteria has greater than 50% 33% identity two [corrected] bacterial hydroxamate-type Fe(III)-siderophores. dendrogram describing total inferred among 36 TonB-dependent constructed; grouped Fe(III)-hydroxamate receptors. The transcriptional start site fegA mapped by primer extension analysis, Fur-binding found promoter. Primer RNA slot blot analysis demonstrated that expressed only cells grown under iron-limiting conditions. This first report cloning gene encoding receptor rhizobia.