We have isolated mutations in rpoA, the gene encoding the a subunit of RNA polymerase, that specifically affect transcriptional control by OmpR and EnvZ, the two-component regulatory system that controls porin gene expression in Escherichia coli. Characterization of these mutations and a previously isolated rpoA allele suggests that both positive and negative regulation of porin gene transcript...

The porin from Paracoccus denitrificans ATCC 13543 was purified and crystallized. Two crystal forms were obtained from porin solutions with beta-d-octylglucopyranoside as detergent. Crystals of form I belong to the monoclinic spacegroup C2 with unit cell dimensions a = 112.2 A, b = 193.8 A, c = 100.5 A and beta = 129.2 degrees. There is 1 trimer per asymmetric unit. Crystals of form II are tric...

Mycobacteria have low-permeability outer membranes that render them resistant to most antibiotics. Hydrophilic nutrients can enter by way of transmembrane-channel proteins called porins. An x-ray analysis of the main porin from Mycobacterium smegmatis, MspA, revealed a homooctameric goblet-like conformation with a single central channel. This is the first structure of a mycobacterial outer-memb...

The widespread occurrence of dissolved proteins as well as porin proteins was confirmed in water columns at five stations located in the North Pacific, the northern North Pacific, and the Bering Sea, where no investigation has heretofore been made with regard to dissolved protein. The major dissolved proteins detected in this study were determined to be glycosylated, based on the detection of a...

The maltodextrin-specific (malto-)porin from Salmonella typhimurium has been crystallized. Its three-dimensional structure was determined at 2.4 A resolution (1 A = 0.1 nm). A comparison with the structure of the homologous porin from Escherichia coli as well as with the sequences of other related porins showed that there are regions of appreciable sequence and structure variability, despite cl...

We have isolated mutations in rpoA, the gene encoding the alpha subunit of RNA polymerase, that specifically affect transcriptional control by OmpR and EnvZ, the two-component regulatory system that controls porin gene expression in Escherichia coli. Characterization of these mutations and a previously isolated rpoA allele suggests that both positive and negative regulation of porin gene transc...

conclusions although the data support the idea that the basic mechanism of imipenem resistance could be via the loss of oprd, they do not fully explain the role of oprd and indicate that other mechanisms may play an important role. additionally, the significant decrease in the oprd levels in mdr strains suggests that oprd also plays a role in the emergence of both carbapenem and non-carbapenem ...