RgpA and Kgp gingipains are non-covalent complexes of endoprotease catalytic and hemagglutinin-adhesin domains on the surface of Porphyromonas gingivalis. A motif conserved in each domain has been suggested to function as an oligomerization motif. We tested this hypothesis by mutating motif residues to hexahistidine or insertion of hexahistidine tag to disrupt the motif within the Kgp catalytic...

The movement proteins of two tobamoviruses (tobacco mosaic virus, TMV, common strain U1 and cruciferous TMV strain) containing amino-terminal hexahistidine affinity tags were overexpressed in Escherichia coli and purified by metal chelate affinity chromatography. Purified recombinant proteins were immobilized to a Ni(2+)-chelate adsorbent and their ability to interact with full-length genomic T...

Salmonella thin aggregative fimbriae (Tafi; curli) are important in pathogenesis and biofilm formation; however, less is known of their structure and morphogenesis. In the Salmonella agfBAC Tafi operon, the transcription and role of agfC have been elusive. In this study, agfBAC transcripts were detected using a sensitive reverse transcriptase technique. Native AgfC was not detected using polycl...

In the mitochondrial ATP synthase (mtATPase) of the yeast Saccharomyces cerevisiae, the stoichiometry of subunits d, oligomycin-sensitivity conferring protein (OSCP), and b is poorly defined. We have investigated the stoichiometry of these subunits by the application of hexahistidine affinity purification technology. We have previously demonstrated that intact mtATPase complexes incorporating a...

When diphtheria toxin encounters a low pH environment, the channel-forming T domain undergoes a poorly understood conformational change that allows for both its own membrane insertion and the translocation of the toxin's catalytic domain across the membrane. From the crystallographic structure of the water-soluble form of diphtheria toxin, a "double dagger" model was proposed in which two trans...

Herpes simplex virus 1 (HSV-1) ICP27 and ICP8 proteins have both been implicated in the transcription of late genes and regulation of viral gene expression. We showed previously that ICP27 and ICP8 associate with the RNAP II holoenzyme (Zhou and Knipe, J. Virol. 76, 5893-5904). Here, we demonstrate that ICP27 and ICP8 coprecipitate from lysates of HSV-1-infected HEp2 cells and from lysates of i...

BACKGROUND The detection of unknown mutations is important in research and medicine. For this purpose, a mismatch-specific endonuclease CEL I from celery has been established as a useful tool in high throughput projects. Previously, CEL I-like activities were described only in a variety of plants and could not be expressed in an active form in bacteria. RESULTS We describe expression of activ...

Precursor protein translocation across the Escherichia coli inner membrane is mediated by the translocase, which is composed of a heterotrimeric integral membrane protein complex with SecY, SecE, and SecG as subunits and peripherally bound SecA. Cross-linking experiments were conducted to study which proteins are associated with SecA in vivo. Formaldehyde treatment of intact cells results in th...

Bacterial cell surface display is a widely used technology for bioadsorption and for the development of a variety of screening systems. Magnetotactic bacteria are unique species of bacteria due to the presence of magnetic nanoparticles within them. These intracellular, nanosized (50 to 100 nm) magnetic nanoparticles enable the cells to migrate and be manipulated by magnetic force. In this work,...

Escherichia coli K1 is a leading pathogen in neonatal sepsis and meningitis. The K1 capsule, composed of alpha2,8-linked polysialic acid, represents the major virulence factor. In some K1 strains, phase-variable O-acetylation of the capsular polysaccharide is observed, a modification that is catalyzed by the prophage-encoded O-acetyltransferase NeuO. Phase variation is mediated by changes in th...