Two-dimensional polyacrylamide gel electrophoresis isolation and microsequencing of Pseudomonas aeruginosa proteins

Outer membrane (OM) proteins of beta-lactam-susceptible and -resistant strains of Pseudomonas aeruginosa were analyzed by 2-D polyacrylamide gel electrophoresis. Carrier ampholytes, pH 4-8, and immobilized pH gradient (IPG), pH 3.5-10.0, procedures were used. An acidic-protein spot (pI = 5.2) detected in susceptible but not in an imipenem-resistant strain was sequenced and twenty-five N-terminal amino acids had total homology with the OM protein D, the imipenem-specific porin of P. aeruginosa. A basic-protein spot (pI = 9.0) detected in ceftazidime-resistant, but not in a susceptible strain was sequenced and fourteen N-terminal amino acids had homology with a beta-lactamase encoded by the ampC gene of P. aeruginosa. The IPG procedure allows identification of more than one hundred proteins of the OM fraction from a single gel. Detection of beta-lactamase in OM fractions might reflect a periplasmic contamination, but its anchorage within the OM cannot be ruled out.

Human liver protein map: a reference database established by microsequencing and gel comparison

This publication establishes a reference human liver protein map obtained with immobilized pH gradients. By microsequencing, 57 spots or 42 polypeptide chains were identified. By protein map comparison and matching (liver, red blood cell and plasma sample maps), 8 additional proteins were identified. The new polypeptides and previously known proteins are listed in a table and/or labeled on the protein map, thus providing a human liver two-dimensional gel database. This reference map can be used to identify protein spots on other samples such as rectal cancer biopsies.

Improving the detection of proteins after transfer to polyvinylidene difluoride membranes

N-Terminal sequence analysis of proteins separated by two-dimensional polyacrylamide gel electrophoresis and transferred onto polyvinylidene difluoride (PVDF) membranes has become the method for molecular characterization of proteins contained in biological samples. However, the proteins of lower abundance cannot be sequenced directly, without improving the technique. We have studied a drying method on several PVDF membranes including Trans-Blott, Immobilon P and Problott. Using Amido Black, Coomassie Brilliant Blue R-250 and Ponceau S, we have obtained, in comparison with the non-dried membranes, an enormous increase in the number of detectable proteins.

Plasma protein map: an update by microsequencing

The reference plasma protein map, obtained with immobilized pH gradients in the first dimension of two-dimensional electrophoresis, is presented. By microsequencing, more than 40 polypeptide chains were identified. The new polypeptides and previously known proteins are listed in a table and labeled on the protein map, thus providing an update of the human plasma two-dimensional gel database.