The localization of the reaction center polypeptides (L, M, and H) in the membranes of both the wild-type, strain 2.4.1, and the carotenoidless mutant, R-26, of Rhodopseudomonas sphaeroides was determined by using affinity-purified antibodies specific for these proteins. Binding of the antibodies to reaction center subunits in spheroplasts was visualized in the electron microscope by immunoferr...

Drugs and certain proteins are transported across the membranes of Gram-negative bacteria by energy-activated pumps. The outer membrane component of these pumps is a channel that opens from a sealed resting state during the transport process. We describe two crystal structures of the Escherichia coli outer membrane protein TolC in its partially open state. Opening is accompanied by the exposure...

The Escherichia coli TolC protein is central to toxin export and drug efflux across the inner and outer cell membranes and the intervening periplasmic space. The crystal structure has revealed that TolC assembles into a remarkable α-helical trans-periplasmic cylinder (tunnel) embedded in the outer membrane by a contiguous β-barrel (channel), so providing a large duct open to the outside environ...

The periodontopathic bacterium Actinobacillus actinomycetemcomitans possesses a 35-kDa periplasmic iron-repressible protein. Its regulation is mediated by the Fur protein, as was inferred from the Fur-binding consensus sequence at the -35 position of the gene for the 35-kDa protein and from the relaxed expression of the gene in a mutant with an altered Fur-binding sequence. The 35-kDa protein, ...

O-glycosylation has been considered a limiting factor in protein secretion in filamentous fungi. Overexpression of the yeast DPM1 gene encoding dolichylphosphate mannose synthase (DPMS) in an Aspergillus nidulans mutant (BWB26A) deficient in O-glycosylation caused an increase in the number of secretory vesicles and changes in protein secretion. However, the secretory proteins, primarily O-manno...

Hydropathy profile analyses of the amino acid sequence of the quorum-sensing hybrid histidine kinase LuxN of Vibrio harveyi predict a periplasmic location of the N terminus. To test this, two-hybrid proteins consisting of LuxN and an N-terminally fused maltose-binding protein with or without a leader sequence were analyzed with regard to the enzymatic activities of LuxN, protease accessibility,...

The locations of cytochrome cd1 nitrite reductases in Pseudomonas aeruginosa and Pseudomonas fluorescens and copper nitrite reductases in Achromobacter cycloclastes and Achromobacter xylosoxidans were identified. Immunogold labeling with colloidal-gold probes showed that the nitrite reductases were synthesized exclusively in anaerobically grown (denitrifying) cells. Little immunogold label occu...

Secretins form megadalton bacterial-membrane channels in at least four sophisticated multiprotein systems that are crucial for translocation of proteins and assembled fibers across the outer membrane of many species of bacteria. Secretin subunits contain multiple domains, which interact with numerous other proteins, including pilotins, secretion-system partner proteins, and exoproteins. Our und...

Hydrolysis of sugar phosphates by crude and purified preparations of periplasmic hexose phosphatase from Salmonella typhimurium followed Michaelis-Menten kinetics. The enzyme bound glucose 1-phosphate with high affinity (Km = 10 microM) but bound glucose 6-phosphate with low affinity (Km = 2,000 microM). The order of substrate affinities was glucose 1-phosphate greater than mannose 1-phosphate ...

In Escherichia coli cells carrying wild-type ovalbumin cDNA, some of the recombinant protein was secreted into the periplasmic space. In contrast, a signal-region mutant form of ovalbumin (deletion, Gly1 to Ala39) was not detected in the periplasm despite being synthesized at the same level as the wild-type protein. Chemical and spectroscopic analyses showed that periplasmic ovalbumin assumes a...