Mechanism of Action of Nikkomycin and the Peptide Transport System of Candida albicans

ABSTRACT Mycoplasma hominis, a cell-wall-less prokaryote, was shown to be cytoadherent by the participation of a 100-kDa membrane protein (P100). To identify the gene encoding P100, peptides of P100 were partially sequenced to enable the synthesis of P100-specific oligonucleotides suitable as probes for the detection of the P100 gene. With this strategy, we identified a genomic region of about 10.4 kb inM. hominis FBG carrying the P100 gene. Analysis of the complete deduced protein sequence suggests that P100 is expressed as a pre-lipoprotein with a structure in the N-terminal region common to peptide-binding proteins and an ATP- or GTP-binding P-loop structure in the C-terminal region. Downstream of the P100 gene, an additional four open reading frames putatively encoding the four core domains of an active transport system, OppBCDF, were localized. The organization of the P100 gene and oppBCDF in a transcriptionally active operon structure was demonstrated in Northern blot and reverse transcription-PCR analyses, as all gene-specific probes detected a common RNA of 9.5 kb. Primer extension analysis revealed that the transcriptional initiation site was localized 323 nucleotides upstream of the methionine-encoding ATG of the P100 gene. The peptide-binding character of the P100 protein was confirmed by fluorescence spectroscopy and strongly suggests that the cytoadherence-mediating lipoprotein P100 represents OppA, the substrate-binding domain of a peptide transport system in M. hominis.

Download Full-text

Utilization of Oligopeptides by Listeria monocytogenes Scott A

Applied and Environmental Microbiology ◽

10.1128/aem.64.3.1059-1065.1998 ◽

1998 ◽

Vol 64 (3) ◽

pp. 1059-1065 ◽

Cited By ~ 31

Author(s):

Annette Verheul ◽

Frank M. Rombouts ◽

Tjakko Abee

Keyword(s):

Listeria Monocytogenes ◽

Transport System ◽

Growth Stimulation ◽

Sole Source ◽

Fermented Milk ◽

Defined Medium ◽

Peptide Transport ◽

Transport Systems ◽

Oligopeptide Transport System ◽

Oligopeptide Transport

ABSTRACT For effective utilization of peptides, Listeria monocytogenes possesses two different peptide transport systems. The first one is the previously described proton motive force (PMF)-driven di- and tripeptide transport system (A. Verheul, A. Hagting, M.-R. Amezaga, I. R. Booth, F. M. Rombouts, and T. Abee, Appl. Environ. Microbiol. 61:226–233, 1995). The present results reveal that L. monocytogenes possesses an oligopeptide transport system, presumably requiring ATP rather than the PMF as the driving force for translocation. Experiments to determine growth in a defined medium containing peptides of various lengths suggested that the oligopeptide permease transports peptides of up to 8 amino acid residues. Peptidase activities towards several oligopeptides were demonstrated in cell extract from L. monocytogenes, which indicates that upon internalization, the oligopeptides are hydrolyzed to serve as sources of amino acids for growth. The peptide transporters of the nonproteolytic L. monocytogenes might play an important role in foods that harbor indigenous proteinases and/or proteolytic microorganisms, since Pseudomonas fragi as well as Bacillus cereus was found to enhance the growth ofL. monocytogenes to a large extent in a medium in which the milk protein casein was the sole source of nitrogen. In addition, growth stimulation was elicited in this medium when casein was hydrolyzed by using purified protease from Bacillus licheniformis. The possible contribution of the oligopeptide transport system in the establishment of high numbers of L. monocytogenes cells in fermented milk products is discussed.

Download Full-text