A @entity1446 -responsive regulator controls synthesis of XXXX in @entity794 .

@entity794 @entity73350 @entity73351 @entity3338 @entity68 @entity1446
UNASSIGNED: @entity794 possesses a multitude of mechanisms by which it can obtain @entity68 during growth under @entity68 starvation conditions. It expresses an effective @entity1446 acquisition system (the @entity68 -regulated surface determinant system), it produces two @entity3338 -type siderophores @entity73350 (SA) and @entity73351 (SB), and it expresses transporters for many other siderophores that it itself does not synthesize. The Ferric Uptake Regulator, or Fur, protein regulates expression of genes encoding all of these systems. Mechanisms of fine-tuning expression of @entity68 -regulated genes, beyond simple @entity68 -regulation via Fur, have not been uncovered in this organism. Here, we identify the ninth gene of the sbn operon, sbnI, as encoding a ParB/Spo0J-like protein that is required for expression of genes in the sbn operon from sbnD onwards. Expression of sbnD-I is drastically decreased in an sbnI mutant, and the mutant does not synthesize detectable SB during early phases of growth. Thus, SB-mediated @entity68 acquisition is impaired in an sbnI mutant strain. We show that the protein forms dimers and tetramers in solution and binds to DNA within the sbnC coding region. Moreover, we show that SbnI binds @entity1446 , and that @entity1446 -bound SbnI does not bind DNA. Last, we show that providing exogenous @entity1446 to @entity794 growing in an @entity68 -free medium results in delayed synthesis of SB. This is the first study in @entity794 that identifies a DNA-binding regulatory protein that senses @entity1446 to control gene expression for siderophore synthesis.
