Molecular characterization and functional analysis of a secA gene homolog in Actinobacillus actinomycetemcomitans.
Results of Southern blot analyses and polymerase chain reaction revealed that the Gram-negative pathogen, Actinobacillus actinomycetemcomitans, harbored DNA homologous to the secA gene of Escherichia coli. In E. coli, the secA gene product is essential for translocation of proteins across the inner membrane via the Sec system. This A. actinomycetemcomitans secA homolog was cloned and its nucleotide sequence determined. Amino acid sequence analysis of the cloned gene revealed significant homology to the SecA proteins of Haemophilus influenzae, E. coli, Caulobacter crescentus and Bacillus subtilis. Although the cloned gene did not complement a temperature sensitive mutation in the E. coli secA gene, strains harboring the cloned gene did produce a protein that cross-reacted with anti-SecA antibody. In addition, the cloned gene did restore sensitivity to sodium azide in an E. coli azide mutant. These data support the hypothesis that A. actinomycetemcomitans may use a system similar to the Sec system of E. coli to transport proteins across the cytoplasmic membrane, but suggest that the A. actinomycetemcomitans gene product may require genera-specific Sec proteins to complement some Sec mutations in E. coli.
Novak
K F
KF
Department of Dental Public Health, University of Pittsburgh School of Dental Medicine, PA 15261, USA. kfn+@pitt.edu
Nonnemacher
M R
MR
Pourhamidi
J
J
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016976:Aggregatibacter actinomycetemcomitans / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins