Gonococcal transferrin-binding protein 1 is required for transferrin utilization and is homologous to TonB-dependent outer membrane receptors.
The pathogenic Neisseria species are capable of utilizing transferrin as their sole source of iron. A neisserial transferrin receptor has been identified and its characteristics defined; however, the biochemical identities of proteins which are required for transferrin receptor function have not yet been determined. We identified two iron-repressible transferrin-binding proteins in Neisseria gonorrhoeae, TBP1 and TBP2. Two approaches were taken to clone genes required for gonococcal transferrin receptor function. First, polyclonal antiserum raised against TBP1 was used to identify clones expressing TBP1 epitopes. Second, a wild-type gene copy was cloned that repaired the defect in a transferrin receptor function (trf) mutant. The clones obtained by these two approaches were shown to overlap by DNA sequencing. Transposon mutagenesis of both clones and recombination of mutagenized fragments into the gonococcal chromosome generated mutants that showed reduced binding of transferrin to whole cells and that were incapable of growth on transferrin. No TBP1 was produced in these mutants, but TBP2 expression was normal. The DNA sequence of the gene encoding gonococcal TBP1 (tbpA) predicted a protein sequence homologous to the Escherichia coli and Pseudomonas putida TonB-dependent outer membrane receptors. Thus, both the function and the predicted protein sequence of TBP1 were consistent with this protein serving as a transferrin receptor.
Cornelissen
C N
CN
Department of Medicine, School of Medicine, University of North Carolina, Chapel Hill 27599.
Biswas
G D
GD
Tsai
J
J
Paruchuri
D K
DK
Thompson
S A
SA
Sparling
P F
PF
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D005816:Genetic Complementation Test; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology; D033862:Iron-Binding Proteins; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009344:Neisseria gonorrhoeae / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011990:Receptors, Transferrin / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic / Q000187:drug effects; D014168:Transferrin / Q000378:metabolism*; D033863:Transferrin-Binding Proteins
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D033862:Iron-Binding Proteins; D008565:Membrane Proteins; D011990:Receptors, Transferrin; D014168:Transferrin; D033863:Transferrin-Binding Proteins; C057616:tonB protein, Bacteria; C489181:tonB protein, E coli; D007501:Iron