Ra. Larsen et al., IDENTIFICATION OF TONB HOMOLOGS IN THE FAMILY ENTEROBACTERIACEAE AND EVIDENCE FOR CONSERVATION OF TONB-DEPENDENT ENERGY TRANSDUCTION COMPLEXES, Journal of bacteriology, 178(5), 1996, pp. 1363-1373
The transport of Fe(III)-siderophore complexes and vitamin B-12 across
the outer membrane of Escherichia coli requires the TonB-dependent en
ergy transduction system, A set of murine monoclonal antibodies (MAbs)
was generated against an E. coli TrpC-TonB fusion protein to facilita
te structure and function studies, In the present study, the epitopes
recognized by these MAbs were mapped, and their distribution in gram-n
egative organisms was examined, Cross-species reactivity patterns obta
ined against TonB homologs of known sequence were used to refine epito
pe mapping, with some epitopes ultimately confirmed by inhibition expe
riments using synthetic polypeptides. Epitopes recognized by this set
of MAbs were conserved in TonB homologs for 9 of 12 species in the fam
ily Enterobacteriaceae (including E. coli), including previously unide
ntified TonB homologs in Shigella, Citrobacter, Proteus, and Kluyvera
species, These homologs were also detected by a polyclonal alpha-TrpC-
TonB serum that additionally recognized the known Yersinia enterocolit
ica TonB homolog and a putative TonB homolog in Edwardsiella tarda, Th
ese antibody preparations failed to detect the known TonB homologs of
either Pseudomonas putida or Haemophilus influenzae but did identify p
otential TonB homologs in several other nonenteric gram-negative speci
es, In vivo chemical cross-linking experiments demonstrated that in ad
dition to TonB, auxiliary components of the TonB-dependent energy tran
sduction system are broadly conserved in members of the family Enterob
acteriaceae, suggesting that the TonB system represents a common syste
m for high-affinity active transport across the gram-negative outer me
mbrane.