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1.
Fig. 5.

Fig. 5. From: Gram-positive three-component antimicrobial peptide-sensing system.

Antimicrobial resistance conferred by the aps system. Killing assays of WT, aps deletion, genetically complemented, and respective control strains with the cloning vector are shown.

Min Li, et al. Proc Natl Acad Sci U S A. 2007 May 29;104(22):9469-9474.
2.
Fig. 4.

Fig. 4. From: Gram-positive three-component antimicrobial peptide-sensing system.

Specificity of the aps response for cationic AMPs. Quantitative RT-PCR measurements of the dltB target gene under the influence of subinhibitory concentrations of various AMPs in the WT and apsS deletion strains are shown. ∗∗∗, P < 0.001; ∗∗, P < 0.01 vs. corresponding sample without peptide. For most peptides, concentrations were the same as for hBD3 (2 μM, which is ≈10 μg/ml for hBD3). Because of significant killing activity at this concentration, lower concentrations were used for brevinin (1 μM) and nisin (0.1 μM).

Min Li, et al. Proc Natl Acad Sci U S A. 2007 May 29;104(22):9469-9474.
3.
Fig. 2.

Fig. 2. From: Gram-positive three-component antimicrobial peptide-sensing system.

Phenotypes of aps deletion mutant strains. (A) In vitro growth of aps deletion, complemented, and respective control strains in TSB media. (B) Zymographic analysis of bacteriolytic enzymes in cell surface extracts of WT and aps deletion strains. Equal amount of protein was added to each lane. (C) Quantitative RT-PCR of major autolysin atlE expression (at 12 h of growth) in WT and aps deletion strains.

Min Li, et al. Proc Natl Acad Sci U S A. 2007 May 29;104(22):9469-9474.
4.
Fig. 1.

Fig. 1. From: Gram-positive three-component antimicrobial peptide-sensing system.

Gene regulatory responses of S. epidermidis to the antimicrobial peptide hBD3. (A) Quantitative RT-PCR of selected genes from Table 1. (B) Arrangement of aps and vraFG-homologous genes in the S. epidermidis genome. (C) Quantitative RT-PCR of the two hBD3-regulated target genes dltB and mprF in WT, apsS deletion, genetically complemented apsS deletion, and respective control strains. (D) Quantitative RT-PCR of the two hBD3-regulated target genes dltB and mprF in WT, apsS, apsR, and apsX deletion strains. hBD3 was used at the subinhibitory concentration of 10 μg/ml in all experiments. ∗, P < 0.05; ∗∗, P < 0.01; ∗∗∗, P < 0.001, vs. corresponding data without hBD3.

Min Li, et al. Proc Natl Acad Sci U S A. 2007 May 29;104(22):9469-9474.
5.
Fig. 6.

Fig. 6. From: Gram-positive three-component antimicrobial peptide-sensing system.

The aps system. Model of aps function and regulated target mechanisms. Cationic AMPs that usually function by pore formation in the cytoplasmic membrane (shown on the right), bind to the anionic loop of ApsS (left) and trigger activation of the aps system (gray), leading to activation of aps-regulated target mechanisms: (i) d-alanylation of teichoic acids by the dlt system (purple), (ii) lysylination of phospholipids by MprF (yellow), and (iii) putative transport of AMPs through an ABC transporter (blue). The transporter may work either by expelling the pore-forming peptides from the membrane or by importing them into the cell for proteolytic inactivation. ApsX does not contain a putative signal peptide sequence (Signal P software, Version 3.0; Technical University of Denmark, www.cbs.dtu.dk). It contains a possible transmembrane sequence at the very C terminus with most of the protein predicted to be cytoplasmic. It was therefore drawn as cytoplasmic, but membrane-attached.

Min Li, et al. Proc Natl Acad Sci U S A. 2007 May 29;104(22):9469-9474.
6.
Fig. 3.

Fig. 3. From: Gram-positive three-component antimicrobial peptide-sensing system.

Role of the ApsS extracellular loop in antimicrobial peptide binding. (A) Amino acid sequence of the ApsS sensor showing the locations of transmembrane and extracellular loop segments. Negatively charged amino acids in the extracellular loop are marked. (B) Reaction of antiserum with total cell extracts of WT and apsS deletion strains. (C) Subcellular location of ApsS. The membrane fraction was prepared by ultracentrifugation for 90 min at 105,000 × g and resuspending the pellet in buffer containing 1% Triton X-100. The supernatant yielded the cytoplasmic fraction, whereas still insoluble material was again centrifuged and directly resuspended in SDS/PAGE loading buffer. (D) Quantitative RT-PCR of dltB gene expression in S. epidermidis WT strain. Samples were incubated with different antiserum concentrations in 10 mM PBS/100 mM NaCl for 1 h before hBD3 at 10 μg/ml was added, and samples were incubated for 3 h more before RNA isolation. In all experiments, cells were harvested at OD600 nm = 3 after inoculation from a preculture grown overnight. ∗∗∗, P < 0.001 vs. sample without antiserum.

Min Li, et al. Proc Natl Acad Sci U S A. 2007 May 29;104(22):9469-9474.

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