Biomedical subjects

J J Barondess

Publications and source records attributed to J J Barondess.

5 recordsLinked to original sources

PubMed1995

bor gene of phage lambda, involved in serum resistance, encodes a widely conserved outer membrane lipoprotein.

bor is one of two recently identified genes of phage lambda which are expressed during lysogeny and whose products display homology to bacterial virulence proteins. bor is closely related to the iss locus of plasmid CoIV,I-K94, which promotes bacterial resistance to serum complement killing in vitro and virulence in animals. bor has a similar in vitro effect. We show here that the bor gene product is a lipoprotein located in the Escherichia coli outer membrane. We also find that antigenically related proteins are expressed by lysogens of a number of other lambdoid coliphage, in cells carrying the cloned iss gene, and in several clinical isolates of E. coli. These results demonstrate that bor sequences are widespread and present a starting point for mechanistic analysis of bor-mediated serum resistance.

Amino Acid Sequence↗

PubMed1992

FtsL, an essential cytoplasmic membrane protein involved in cell division in Escherichia coli.

We have identified a gene involved in bacterial cell division, located immediately upstream of the ftsI gene in the min 2 region of the Escherichia coli chromosome. This gene, which we named ftsL, was detected through characterization of TnphoA insertions in a plasmid containing this chromosomal region. TnphoA topological analysis and fractionation of alkaline phosphatase fusion proteins indicated that the ftsL gene product is a 13.6-kDa cytoplasmic membrane protein with a cytoplasmic amino terminus, a single membrane-spanning segment, and a periplasmic carboxy terminus. The ftsL gene is essential for cell growth and division. A null mutation in ftsL resulted in inhibition of cell division, formation of long, nonseptate filaments, ultimate cessation of growth, and lysis. Under certain growth conditions, depletion of FtsL or expression of the largest ftsL-phoA fusion produced a variety of cell morphologies, including Y-shaped bacteria, indicating a possible general weakening of the cell wall. The FtsL protein is estimated to be present at about 20 to 40 copies per cell. The periplasmic domain of the protein displays a sequence with features characteristic of leucine zippers, which are involved in protein dimerization.

Amino Acid Sequence↗

PubMed1990

A bacterial virulence determinant encoded by lysogenic coliphage lambda.

Although phage lambda represents a well studied biological systems, it has certain features that remain obscure. Among these is the function of the roughly one third of the phage genome dispensable for growth in the laboratory, yet retained despite undoubted pressure to economize. Here we report that these 'accessory' sequences contain two genes which are expressed during lysogeny, and encode host-cell envelope proteins. One of these is lom, the product of which is found in the bacterial outer membrane, and is homologous to virulence proteins of two other enterobacterial genera. The other gene, previously unidentified, we designate bor. Expression of bor significantly increases the survival of the Escherichia coli host cell in animal serum. This property is a well known bacterial virulence determinant--indeed, bor and its adjacent sequences are highly homologous to the iss serum resistance locus of the plasmid ColV2-K94, which confers virulence in animals. These results show that the lambda prophage is more transcriptionally active than has long been assumed, and suggest that lysogeny may generally have a role in bacterial survival in animal hosts, and perhaps in pathogenesis.

Alkaline Phosphatase↗

PubMed1975

Studies on the control of antibody synthesis. VII. Change in affinity of direct and indirect plaque-forming cells with time after immunization in the mouse: loss of high affinity plaques late after immunization.

The change in avidity of anti-hapten antibody with time after immunization was studied in mice at the level of the antibody-forming cell. A progressive increase in avidity was seen in both direct and indirect plaque-forming cells. Late (38 days) after immunization with a large dose of antigen there was a preferential loss of high avidity plaque-forming cells and the average avidity decreased. High avidity memory cells were still present since boosting resulted in the prompt appearance of very high avidity plaque-forming cells. There was a strong positive correlation between the avidity of the direct and the indirect plaque-forming cells present in the same spleen. A pattern of change in avidity and heterogeneity of avidity similar to that observed with intact animals was seen in lethally irradiated mice reconstituted with normal spleen and thymus cells.

Animals↗

PubMedDate not supplied

Alkaline phosphatase fusions in the study of cell division genes.

Alkaline phosphatase fusions have been used to analyse plasmid- or phage-carried genes from the two-minute region of the Escherichia coli chromosome. These studies have revealed the following: 1) Bacteriophage lambda carries two genes for cell envelope proteins, lom and bor, that are expressed in lysogens and probably contribute to the pathogenicity of its E. coli host. 2) The ftsQ and ftsl gene products are integral proteins of the cytoplasmic membrane with small cytoplasmic domains and large periplasmic domains. 3) The ftsQ and ftsl gene products are made in very small amounts, on the order of 25 molecules per cell. 4) The ftsQ gene product is essential for cell growth and is required throughout the formation of the cell septum. 5) An open reading frame just upstream from ftsl, thought to be involved in cell division, is expressed and probably codes for a cytoplasmic membrane protein.

Alkaline Phosphatase↗