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B Lipinska

Publications and source records attributed to B Lipinska.

12 recordsLinked to original sources
PubMed1992

When Greta Garbo is easier to remember than Stefan Edberg: influences of prior knowledge on recognition memory in Alzheimer's disease.

This study investigated the effects of prior knowledge on recognition memory in patients with a mild Alzheimer's disease. Normal older adults and mildly demented patients were presented with dated and contemporary famous faces with name tags and were asked to generate unique statements about each person. Results indicated that both groups generated more statements about the dated than about the contemporary figures. Most important, both groups performed better with the dated than with the contemporary faces in an unexpected episodic face recognition task. This pattern of results suggests that both groups (a) possess more knowledge of dated than of contemporary famous individuals and (b) are able to utilize prior knowledge to enhance episodic remembering. Viewing these results in light of other recent work, it is concluded that differences between normal old and mildly demented individuals in the ability to utilize cognitive support for remembering may be differences in degree.

Aged↗
PubMed1992

arc-dependent thermal regulation and extragenic suppression of the Escherichia coli cytochrome d operon.

In a screen for Escherichia coli genes whose products are required for high-temperature growth, we identified and characterized a mini-Tn10 insertion that allows the formation of wild-type-size colonies at 30 degrees C but results in microcolony formation at 36 degrees C and above (Ts- phenotype). Mapping, molecular cloning, and DNA sequencing analyses showed that the mini-Tn10 insertion resides in the cydB gene, the distal gene of the cydAB operon (cytochrome d). The Ts- growth phenotype was also shown to be associated with previously described cyd alleles. In addition, all cyd mutants were found to be extremely sensitive to hydrogen peroxide. Northern (RNA) blot analysis showed that cyd-specific mRNA levels accumulate following a shift to high temperature. Interestingly, this heat shock induction of the cyd operon was not affected in an rpoH delta background but was totally absent in an arcA or arcB mutant background. Extragenic suppressors of the Cyd Ts- phenotype are found at approximately 10(-3). Two extragenic suppressors were shown to be null alleles in either arcA or arcB. One interpretation of our results is that in the absence of ArcA or ArcB, which are required for the repression of the cyo operon (cytochrome o), elevated levels of Cyo are produced, thus compensating for the missing cytochrome d function. Consistent with this interpretation, the presence of the cyo gene on a multicopy plasmid suppressed the Ts- and hydrogen peroxide-sensitive phenotypes of cyd mutants.

Bacterial Outer Membrane Proteins↗
PubMed1991

Identification of the Escherichia coli sohB gene, a multicopy suppressor of the HtrA (DegP) null phenotype.

We cloned and sequenced the sohB gene of Escherichia coli. The temperature-sensitive phenotype of bacteria that carry a Tn10 insertion in the htrA (degP) gene is relieved when the sohB gene is present in the cell on a multicopy plasmid (30 to 50 copies per cell). The htrA gene encodes a periplasmic protease required for bacterial viability only at high temperature, i.e., above 39 degrees C. The sohB gene maps to 28 min on the E. coli chromosome, precisely between the topA and btuR genes. The gene encodes a 39,000-Mr precursor protein which is processed to a 37,000-Mr mature form. Sequencing of a DNA fragment containing the gene revealed an open reading frame which could encode a protein of Mr 39,474 with a predicted signal sequence cleavage site between amino acids 22 and 23. Cleavage at this site would reduce the size of the processed protein to 37,474 Mr. The predicted protein encoded by the open reading frame has homology with the inner membrane enzyme protease IV of E. coli, which digests cleaved signal peptides. Therefore, it is possible that the sohB gene encodes a previously undiscovered periplasmic protease in E. coli that, when overexpressed, can partially compensate for the missing HtrA protein function.

Amino Acid Sequence↗
PubMed1990

Mutational analysis of the phage T4 morphogenetic 31 gene, whose product interacts with the Escherichia coli GroEL protein.

The phage T4 morphogenetic gene 31 has been sequenced. Its deduced gene product is a polypeptide of 111 aa, with a predicted Mr of 12064 and a pI of 4.88. The proof that the assigned open reading frame (ORF) encodes Gp31 rests on the sequencing of two known gene 31 amber mutations, amN54 and NG71, demonstrating that these mutations result in translational termination within the assigned ORF. Furthermore, the sequencing of four different T4 epsilon mutations, isolated on the basis of allowing the phage to propagate on Escherichia coli groEL- hosts, showed that they are either missense mutations or 3-bp deletions in the gene 31 reading frame. The sequencing of neighboring DNA revealed the presence of five other ORFs, one of which overlaps gene 31 substantially, but in the opposite orientation.

Amino Acid Sequence↗
PubMed1990

The HtrA (DegP) protein, essential for Escherichia coli survival at high temperatures, is an endopeptidase.

As a preliminary step in the understanding of the function of the Escherichia coli HtrA (DegP) protein, which is indispensable for bacterial survival only at elevated temperatures, the protein was purified and partially characterized. The HtrA protein was purified from cells carrying the htrA gene cloned into a multicopy plasmid, resulting in its overproduction. The sequence of the 13 N-terminal amino acids of the purified HtrA protein was determined and was identical to the one predicted for the mature HtrA protein by the DNA sequence of the cloned gene. Moreover, the N-terminal sequence showed that the 48-kilodalton HtrA protein is derived by cleavage of the first 26 amino acids of the pre-HtrA precursor polypeptide and that the point of cleavage follows a typical target sequence recognized by the leader peptidase enzyme. The HtrA protein was shown to be a specific endopeptidase which was inhibited by diisopropylfluorophosphate, suggesting that HtrA is a serine protease.

Amino Acid Sequence↗
PubMed1989

Cloning and identification of bacteriophage T4 gene 2 product gp2 and action of gp2 on infecting DNA in vivo.

We sequenced bacteriophage T4 genes 2 and 3 and the putative C-terminal portion of gene 50. They were found to have appropriate open reading frames directed counterclockwise on the T4 map. Mutations in genes 2 and 64 were shown to be in the same open reading frame, which we now call gene 2. This gene codes for a protein of 27,068 daltons. The open reading frame corresponding to gene 3 codes for a protein of 20,634 daltons. Appropriate bands on polyacrylamide gels were identified at 30 and 20 kilodaltons, respectively. We found that the product of the cloned gene 2 can protect T4 DNA double-stranded ends from exonuclease V action.

Amino Acid Sequence↗
PubMed1989

Identification, characterization, and mapping of the Escherichia coli htrA gene, whose product is essential for bacterial growth only at elevated temperatures.

We identified and cloned an Escherichia coli gene called htrA (high temperature requirement). The htrA gene was originally discovered because mini-Tn10 transposon insertions in it allowed E. coli growth at 30 degrees C but prevented growth at elevated temperatures (above 42 degrees C). The htrA insertion mutants underwent a block in macromolecular synthesis and eventually lysed at the nonpermissive temperature. The htrA gene was located at approximately 3.7 min (between the fhuA and dapD loci) on the genetic map of E. coli and between 180 and 187.5 kilobases on the physical map. It coded for an unstable, 51-kilodalton protein which was processed by removal of an amino-terminal fragment, resulting in a stable, 48-kilodalton protein.

Chromosome Mapping↗
PubMed1988

Sequence analysis and regulation of the htrA gene of Escherichia coli: a sigma 32-independent mechanism of heat-inducible transcription.

Previous work has established that the E. coli htrA gene product is essential for bacterial survival at temperatures above 42 degrees. We have sequenced the htrA gene region and found an open reading frame (ORF) coding for a protein of 491 amino acids with a calculated molecular weight of 51,163 daltons. This molecular weight corresponds well with that seen following electrophoresis on SDS-polyacrylamide gels. This protein has an amino-terminal sequence typical for a leader peptide and undergoes post-translational modification by cleavage of an amino-terminal portion. The insertional mutations which affect the function of the htrA gene map inside this ORF. The levels of htrA mRNA increase rapidly and transiently upon heat shock in a manner independent of the rpoH gene, which encodes the sigma 32 RNA polymerase subunit and is known to regulate transcription of typical heat shock genes. Using S1 mapping and RNA primer extension, we have identified the htrA promoter and found that it is similar to the P3 promoter of the rpoH gene. The P3 promoter is especially active at high temperatures and is recognized by a recently identified transcriptional factor, sigma E.

Amino Acid Sequence↗
PubMed1988

Sequence analysis and transcriptional regulation of the Escherichia coli grpE gene, encoding a heat shock protein.

We have sequenced the Escherichia coli grpE gene and shown that it encodes a 197-amino acid residue protein of 21,668-Mr. The predicted N-terminal amino acid sequence, as well as the overall amino acid composition agree well with that of the purified protein. From Northern analysis, we have shown that transcription of the grpE gene is under heat shock regulation, i.e., there is a rapid and transient increase in the rate of synthesis of grpE mRNA upon a shift-up in temperature. Forty-six bases upstream of the structural gene is a sequence closely related to the consensus heat shock promoter identified by Cowing et al. [Proc. Natl. Acad. Sci. U.S.A, 82, 2679-2683]. We have shown by S1 mapping and RNA sequencing that this is indeed the promoter for the grpE mRNA. It appears that all discernable transcription initiates only from this promoter, even under non-heat shock conditions.

Amino Acid Sequence↗
PubMed1981

The R gene product of bacteriophage lambda is the murein transglycosylase.

The radioactively labeled proteins synthesised in Escherichia coli minicells infected by bacteriophage lambda R and lambda R+ were compared by polyacrylamide gel electrophoresis. lambda R mutants, which have lost the ability to lyse host cells, lack a polypeptide of molecular weight 17.5 KD corresponding to the molecular weight of murein transglycosylase - a bacteriolytic enzyme from lambda lysates which we have described previously. It has been shown by direct comparison using radio-labeled enzyme that transglycosylase comigrates with the R gene product. The enzyme was undetectable in induced cultures of E. coli W3350 su degrees (lambda cI857 Ram 5) and C600 (lambda cI857 acR301), while it was present in a lambda Rz mutant lysate. We conclude that the transglycosylase is the R gene product.

Bacteriophage lambda↗