77 SP-Φ-D-TP PBPB1 PBP3 lmo1438 B-5 PBP2b(Spn) 721 79.91 8.26 SP-Φ-D-TP PBPA2 PBP4 lmo2229 A-4 PBP2a(Spn) 714 77.85 6.75 SP-Φ-TG-TP PBPB3 —– lmo0441 B-1 PBP2a(Sau) 678 74.60 6.57 SP-Φ-MecAN-D-TP PBPD1 PBP5 lmo2754 C-T5 PBP3(Spn) 445 48.08 7.63 SP-CP-CA PBPC1 —– lmo0540 C-TH AmpH(Eco) 397 44.53 9.70
SP-BLA PBPC2 —– lmo1916 C-TH R61 (SR61) 335 37.84 7.04 BLA PBPD3 —– lmo1855 M15B —- 274 31.08 5.46 SP-CP(VanY) PBPD2 —– lmo2812 C-T5 PBP5 (Bsu) 272 29.48 4.59 SP(lipo)-CP a Nomenclature of PBPs as defined in ; b Nomenclature of PBPs as defined in [7, 10]; c gene names as identified check details in Listilist web server http://genolist.pasteur.fr/ListiList/; d specific class of PBP as identified in ; edomain structure of PBPs as described in ; SP, signal peptide; Φ, hydrophobic region; TG, transglycosylase domain; TP, transpeptidase domain; D, interaction domain; MecAN, homologous to PBP2a S. aureus resistance protein; CP, carboxypeptidase domain; CA, C-terminal anchor domain; BLA, β-lactamase domain; (VanY), homologous
to VanY; SP(lipo), lipoprotein signal peptide. PBPs form a covalent complex with β-lactam antibiotics . When fluorescent β-lactams are employed, these proteins can be visualized immediately following SDS-PAGE . selleck compound Total protein from whole cells or a cell wall extract of L. monocytogenes EGD were incubated with different concentrations of Boc-FL, Bocillin-650 (Boc-650) or Ampicillin-Alexa430 (Amp-430) for 30 min at 37°C. The highest affinity binding was obtained with Boc-FL and bands identified using this compound in the whole cell assay are shown in Figure 1. PBPs A1, B2, B1, A2, B3, D1, C1 and C2 were also identified with Boc-650 and Amp-430 (data not shown). Two types of non-specific band were also observed (lane 1, 0 μM Boc-FL)
and they represent the natural intrinsic fluorescence of other proteins in the cell extract. However, the bands that are absent in lane 8 (ampicillin 100 μg/ml, 50 μM Boc-FL) compared with lane 7 (50 μM Boc-FL) represent specific PBPs. Those bands that completely disappeared (PBPB1, PBPD1), partially disappeared (PBPA1, PBPB2, PBPA2 Enzalutamide and PBPB3) or remained present (PBPC1 and PBPC2) reflect total, partial and no binding of ampicillin, respectively. The selleck chemical results of an experiment examining saturation with 50 μM Boc-FL, the binding capacity of each PBP for Boc-FL and the affinity of the PBPs for ampicillin (Amp) are presented in Table 2. These assays involved incubation of whole cell with ampicillin followed by a similar incubation with Boc-FL. Therefore, only those PBPs with no or low affinity for ampicillin would be able to bind Boc-FL during the second incubation. The deacylation rate for the PBPs is actually extremely low, which permitted their detection in the gel for several hours after binding. Boc-FL binding to PBPs B1 and D1 was completely inhibited by Amp at 100 μg/ml, and these two PBPs exhibited high (Kd50 = 0.25 μM) and medium (Kd50 = 5.0 μM) affinity for Boc-FL, respectively.