Differential proteomic analysis of the response of Stenotrophomonas maltophilia to imipenem.

This study represents two different large-scale proteomic experiments analyzing the antibiotic response and the mechanisms of production of β-lactamases in the nosocomial pathogen Stenotrophomonas maltophilia. Two-dimensional gel electrophoresis on the cytoplasmic protein fraction, together with iTRAQ® differential labeling and 2-D liquid chromatographic separation (2D-LC) MS/MS on the enriched membrane protein fraction, revealed 73 proteins with a change in abundance upon imipenem challenge. These proteins belong to several different functional pathways.

Mutational analysis of the zinc- and substrate-binding sites in the CphA metallo-beta-lactamase from Aeromonas hydrophila.

The subclass B2 CphA (Carbapenemase hydrolysing Aeromonas) beta-lactamase from Aeromonas hydrophila is a Zn(2+)-containing enzyme that specifically hydrolyses carbapenems. In an effort to evaluate residues potentially involved in metal binding and/or catalysis (His(118), Asp(120), His(196) and His(263)) and in substrate specificity (Val(67), Thr(157), Lys(224) and Lys(226)), site-directed mutants of CphA were generated and characterized. Our results confirm that the first zinc ion is in interaction with Asp(120) and His(263), and thus is located in the 'cysteine' zinc-binding site.

Selectivity of tryptophan residues in mediating photolysis of disulfide bridges in goat alpha-lactalbumin.

Goat alpha-lactalbumin (GLA) contains four tryptophan (Trp) residues and four disulfide bonds. Illumination with near-UV light results in the cleavage of disulfide bridges and in the formation of free thiols. To obtain information about the reaction products, the illuminated protein was carbamidomethylated and digested with trypsin and the peptides were analyzed by mass spectrometry.

Search for substrates for prolyl oligopeptidase in porcine brain.

The function of prolyl oligopeptidase (PO) has been associated with several disorders of the central nervous system. The purpose of this study was to identify endogenous substrates for recombinant porcine PO in porcine brain. The smaller polypeptides were extracted from total brain homogenates and fractionated by two-dimensional chromatography prior to incubation with PO.