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B M Corfe

Publications and source records attributed to B M Corfe.

12 recordsLinked to original sources
PubMed2002

Spore germination.

Despite being relatively insensitive to environmental insult, the spore is responsive to low concentrations of chemical germinants, which induce germination. The process of bacterial spore germination involves membrane permeability changes, ion fluxes and the activation of enzymes that degrade the outer layers of the spore. A number of components in the spore that are required for the germination response have been identified, including a spore-specific family of receptor proteins (the GerA family), an ion transporter and cortex lytic enzymes. The germinant traverses the outer layers of the spore and interacts with its receptor in the inner membrane to initiate the cascade of germination events, but the molecular details of this signal transduction process remain to be identified.

Bacterial Proteins↗
PubMed2001

Cellular damage signals promote sequential changes at the N-terminus and BH-1 domain of the pro-apoptotic protein Bak.

The pro-apoptotic protein Bak is converted from a latent to an active form by damage-induced signals. This process involves an early exposure of an occluded N-terminal epitope of Bak in intact cells. Here we report a subsequent damage-induced change in Bak, detected using an antibody to the central BH-1 domain. Bak co-immunoprecipitated with Bc1-x(L) both in undamaged cells and early after damage, when the N-terminal epitope was exposed but the BH-1 epitope remained occluded. A subsequent decrease in binding of Bak to Bc1-x(L) correlated with exposure of an epitope in the Bak BH-1 domain. Overexpression of Bc1-x(L) did not affect the kinetics of exposure of the Bak N-terminal epitope but delayed exposure of the BH-1 domain. Cytochrome c release from mitochondria facilitates the activation of apoptotic caspases. The majority of cells with exposed Bak BH-1 domains contained cytosolic cytochrome c. However, a small proportion of cells exhibited exposed Bak BH-1 domains that co-localized with mitochondrial cytochrome c. The data are consistent with a two-step model for the activation of Bak by drug-induced damage signals where dissociation of Bc1-x(L) from the BH-1 domain of Bak occurs immediately prior to or concomitantly with cytochrome c release.

Amino Acid Chloromethyl Ketones↗
PubMed2001

Damage-induced Bax N-terminal change, translocation to mitochondria and formation of Bax dimers/complexes occur regardless of cell fate.

Sequential steps in the activation of the pro-apoptotic protein Bax are described for cells with different sensitivity to cytotoxins. SH-EP1 and SH-SY5Y human neuroblastoma cells, derived from a single precursor cell line, differed in their sensitivity to taxol but showed the same sensitivity to cisplatin. Both drugs, in both cell lines, induced exposure of a constitutively occluded N-terminal epitope of Bax. This was reversible and occurred before the translocation of cytosolic Bax to mitochondria. The N-terminal change in Bax, its subsequent movement to mitochondria and its dimerization/complex formation were insufficient for commitment to death, occurring in the same proportion of cells that either maintained (SH-SY5Y) or lost (SH-EP1) clonogenic survival after taxol treatment. Suppression of taxol-induced apoptosis occurred upstream of cytochrome c release from mitochondria in SH-SY5Y cells. The data suggest that a further drug damage-induced event occurs after Bax dimerization/complex formation but prior to cytochrome c release. This event was absent in the taxol-resistant cells.

Antineoplastic Agents↗
PubMed2001

Localization of GerAA and GerAC germination proteins in the Bacillus subtilis spore.

The GerAA, -AB, and -AC proteins of the Bacillus subtilis spore are required for the germination response to L-alanine as the sole germinant. They are likely to encode the components of the germination apparatus that respond directly to this germinant, mediating the spore's response; multiple homologues of the gerA genes are found in every spore former so far examined. The gerA operon is expressed in the forespore, and the level of expression of the operon appears to be low. The GerA proteins are predicted to be membrane associated. In an attempt to localize GerA proteins, spores of B. subtilis were broken and fractionated to give integument, membrane, and soluble fractions. Using antibodies that detect Ger proteins specifically, as confirmed by the analysis of strains lacking GerA and the related GerB proteins, the GerAA protein and the GerAC+GerBC protein homologues were localized to the membrane fraction of fragmented spores. The spore-specific penicillin-binding protein PBP5*, a marker for the outer forespore membrane, was absent from this fraction. Extraction of spores to remove coat layers did not release the GerAC or AA protein from the spores. Both experimental approaches suggest that GerAA and GerAC proteins are located in the inner spore membrane, which forms a boundary around the cellular compartment of the spore. The results provide support for a model of germination in which, in order to initiate germination, germinant has to permeate the coat and cortex of the spore and bind to a germination receptor located in the inner membrane.

Amino Acid Sequence↗
PubMed1999

Cell damage-induced conformational changes of the pro-apoptotic protein Bak in vivo precede the onset of apoptosis.

Investigation of events committing cells to death revealed that a concealed NH2-terminal epitope of the pro-apoptotic protein Bak became exposed in vivo before apoptosis. This occurred after treatment of human Jurkat or CEM-C7A T-lymphoma cells with the mechanistically disparate agents staurosporine, etoposide or dexamethasone. The rapid, up to 10-fold increase in Bak-associated immunofluorescence was measured with epitope-specific monoclonal antibodies using flow cytometry and microscopy. In contrast, using a polyclonal antibody to Bak, immunofluorescence was detected both before and after treatment. There were no differences in Bak protein content nor in subcellular location before or after treatment. Immunofluorescence showed Bcl-xL and Bak were largely associated with mitochondria and in untreated cells they coimmunoprecipitated in the presence of nonioinic detergent. This association was significantly decreased after cell perturbation suggesting that Bcl-xL dissociation from Bak occurred on exposure of Bak's NH2 terminus. Multiple forms of Bak protein were observed by two dimensional electrophoresis but these were unchanged by inducers of apoptosis. This indicated that integration of cellular damage signals did not take place directly on the Bak protein. Release of proteins, including Bcl-xL, from Bak is suggested to be an important event in commitment to death.

Apoptosis↗
PubMed1996

Alanine germination receptors of Bacillus subtilis.

The alanine-stimulated spore germination responses of Bacillus subtilis 168 have been dissected by combining physiological and genetical approaches. From the analyses the authors infer that there are three classes of alanine response. Two of the responses are mediated via the GerA proteins, with and without germinal adjuncts, the third is mediated via the GerB proteins and obligately requires adjuncts.

Alanine↗
PubMed1994

Molecular genetical and phenotypical analysis of the gerM spore germination gene of Bacillus subtilis 168.

The gerM gene, encoding a single product of 22.5 kDa, has been identified by subcloning and sequencing of DNA recovered from adjacent to a Tn917 insertion. The gene product has a potential lipoprotein signal sequence, but otherwise has no homology to known sequences. Spores of the gerM mutant were more heat sensitive than wild-type, but their dipicolinic acid content was normal. The level of cortical peptidoglycan in mutant spores is also normal but release at germination of hexosamine-containing fragments, the breakdown products of cortex degradation, is less complete than wild-type. The sporulation, resistance and germination phenotypes of the gerM mutant would be consistent with the gene product having a role, either directly or indirectly, in peptidoglycan synthesis during sporulation.

Amino Acid Sequence↗
PubMed1994

The gerB region of the Bacillus subtilis 168 chromosome encodes a homologue of the gerA spore germination operon.

Spores of gerB spore germination mutants of Bacillus subtilis 168 are defective in response to the germinative mixture of L-asparagine, glucose, fructose and potassium ions (AGFK), but are normal in the L-alanine (ALA) triggered germination response. A lambda clone of 15 kbp carrying the gerB region has been identified. Sequencing of the gerB region of the clone revealed a cluster of three ORFs encoding putative proteins of 53.3, 41.3 and 42.4 kDa (GerBA, GerBB and GerBC, respectively). The first two of these proteins have substantial hydrophobic regions and the third is a possible lipoprotein. At least two, and probably all three products are required for normal germination in AGFK. The three proteins form a set of homologues of the products of the gerA operon, mutations in which cause a defect in the ALA germination pathway, but cause no defect in AGFK. The GerB proteins show 42%, 31% and 35% identity at the amino-acid level to the corresponding GerA proteins, and the homologues occur in the same order in both operons.

Alleles↗
PubMed1994

Analysis of the expression and regulation of the gerB spore germination operon of Bacillus subtilis 168.

The gerB spore germination operon of Bacillus subtilis 168 is a homologue of the gerA spore germination operon. The expression and regulation of the gerB operon has been examined using a lacZ transcriptional fusion and the transcriptional start defined. The gerB operon is expressed during sporulation under the control of RNA polymerase containing the forespore-specific sigma factor, delta G. This is a further homology to the gerA operon, which is similarly regulated. It is predicted from the localization of expression and the encoded primary sequences that the GerB proteins are located at the inner spore membrane.

Bacillus subtilis↗