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L Lindahl

Publications and source records attributed to L Lindahl.

At least 55 records · Page 3Linked to original sources
PubMed1985

Genetic dissection of stringent control and nutritional shift-up response of the Escherichia coli S10 ribosomal protein operon.

The S10 operon of Escherichia coli is autogenously regulated by L4, one of 11 ribosomal proteins encoded by the operon. We have previously shown that L4 regulates transcription of the operon by modulating the level of read-through at an attenuator in the S10 leader. To determine the physiological roles of both L4-mediated attenuation and the regulation of transcription initiation, we have constructed mutations eliminating their two regulatory targets, the S10 leader and the S10 promoter. Our results indicate that stringent control requires only the S10 promoter and therefore is mediated at the level of initiation. However, growth-medium-dependent control after a nutritional shift-up involves regulation of both initiation of transcription at the promoter and transcription read-through at the attenuator.

Bacterial Proteins↗
PubMed1985

Nucleotide sequence of the alpha ribosomal protein operon of Escherichia coli.

In Escherichia coli some 19 transcription units encoding the 52 ribosomal proteins are scattered throughout the genome. One of the units, the alpha operon, encodes genes for the ribosomal proteins S13, S11, S4 and L17 as well as the alpha subunit of RNA polymerase. We report here the complete 3.0 kb nucleotide sequence of the alpha operon. In addition, we have determined by S1 nuclease mapping the site of transcription termination in this operon.

Amino Acid Sequence↗
PubMed1985

Transcriptional control of the S10 ribosomal protein operon of Escherichia coli after a shift to higher temperature.

In the 5 to 10 min immediately following a shift from 30 to 42 degrees C, the differential synthesis rates of ribosomal proteins encoded by the 11-gene S10 operon are transiently decreased. This effect results largely from a two- to threefold decrease in the differential rate of transcription of the operon. The inhibition of mRNA synthesis is apparently due to two types of control: (i) initiation of transcription at the S10 promoter is inhibited and (ii) readthrough at the attenuator in the S10 leader is decreased. Both of these effects on transcription are independent of the heat shock regulatory gene, htpR. Furthermore, the inhibition of transcription is observed in both relA+ and relA cells, suggesting that the temperature-induced repression does not require the relA-dependent accumulation of guanosine tetraphosphate (ppGpp). However, recovery from the heat shock was slower in relA+ strains than in relA strains. None of the other ribosomal protein operons that we analyzed showed such a strong decrease in transcription after the heat shock.

Escherichia coli↗
PubMed1984

Metal-ion-dependent hydrophobic-interaction chromatography of alpha-lactalbumins.

alpha-Lactalbumins from bovine, human, goat, sheep, and horse milk bind to phenyl-Sepharose in the presence of EDTA and can be eluted by addition of Ca2+ (0.001-100 mM). This property has been utilized to purify these proteins in a one-step purification from milk whey. alpha-Lactalbumin purified in this manner has the same ultraviolet and proton nuclear magnetic resonance spectra as that purified by other methods. Using binding to phenyl-Sepharose as an assay, the conformation of bovine alpha-lactalbumin upon the addition of several metal ions that are known to interact with this protein was investigated. Lanthanides, Mn2+, Mg2+, and Cd2+ can substitute for Ca2+, whereas Zn2+, Al3+, and Co2+ cannot. Surprisingly, whereas lower concentrations of La3+, Mn2+, and Cd2+ (1 mM and less) caused elution from the hydrophobic support, higher concentrations (10 mM) were ineffective. These observations can be rationalized assuming the presence of two distinct metal-ion binding sites with different specificities.

Animals↗
PubMed1984

The nucleotide sequence of the Escherichia coli fus gene, coding for elongation factor G.

We have determined the nucleotide sequence of the Escherichia coli fus gene, which codes for elongation factor G. The protein product of the sequenced gene contains 703 amino acids, with a predicted molecular weight of 77,444. The fus gene shows the nonrandom pattern of codon usage typical of ribosomal proteins and other proteins synthesized at a high level. We have identified several potential promoter sequences within the gene. One of these sequences may correspond to the secondary promoter for expression of the downstream tufA gene (encoding elongation factor Tu) whose activity has been described previously (1,2). A comparison of the nucleotide and amino acid sequences of elongation factors G and Tu reveals a limited but significant homology between the two proteins within the 150 amino acid residues at their amino-terminal ends.

Amino Acid Sequence↗
PubMed1984

Role of attenuation in growth rate-dependent regulation of the S10 r-protein operon of E. coli.

We have investigated the transcription of the 11 gene S10 ribosomal protein operon of Escherichia coli under various growth conditions. The differential synthesis rate of structural gene message increases 2- to 2.5-fold immediately after a shift-up from glycerol minimal medium to glucose plus amino acids. After the initial increase, the transcription rate goes through several oscillations before reaching the new steady-state rate. By comparing the rates of transcription of leader and structural genes, we conclude that these oscillations are due predominantly to changes in the level of read-through at the S10 attenuator. This regulation of attenuation can account for most of the variations in protein synthesis from the S10 operon after a shift. We also measured the level of read-through in cells growing exponentially in different growth media. Over a 2.5-fold range in growth rates, the read-through changed less than 50%. Thus, regulation of attenuation cannot explain the growth-dependent regulation of ribosomal protein synthesis during steady-state growth. Apparently, additional mechanisms are required to control the expression of the S10 operon in exponentially growing cells.

Escherichia coli↗
PubMed1983

Transcription of the S10 ribosomal protein operon is regulated by an attenuator in the leader.

Previous studies have shown that ribosomal protein L4 specifically inhibits the expression of its own operon, the 11-gene S10 operon. To elucidate the mechanism for this regulation, we have examined the effect of protein L4 on transcription of the S10 operon. Hybridization and gel electrophoresis studies indicate that in the presence of excess L4 only RNA molecules about 140 bases long are transcribed from the S10 operon. These short RNA molecules contain the leader, but not structural gene, sequences. Our results suggest that protein L4 stimulates premature termination (attenuation) of transcription about 30 bases upstream from the start of the first structural gene of the S10 operon. The attenuation appears to be independent of the regulation of translation of the operon. We suggest that attenuation of transcription plays a primary role in the autogenous regulation of the S10 operon.

Escherichia coli↗
PubMed1982

A secondary promoter for elongation factor Tu synthesis in the str ribosomal protein operon of Escherichia coli.

The str operon of Escherichia coli contains genes for ribosomal proteins S12 and S7 and for elongation factors EF-G and EF-Tu (Jaskunas et al. 1975). We have subcloned various segments of DNA from this operon onto multicopy plasmids. We found that cells carrying a recombinant plasmid which lacks the major promoter for the str operon but contains the 5' portion of the EF-Tu gene synthesize a novel protein which we have identified as a truncated EF-Tu molecule. Moreover, cells carrying plasmids with an intact EF-Tu gene synthesize the elongation factor at a 3- to 5-fold higher rate than haploid cells. Thus the EF-Tu gene can be expressed in the absence of the major promoter for the str operon. This expression is not due to read-through from plasmid promoters, but it is dependent on the presence of the distal portion of the EF-G gene on the plasmids. These results indicate that there is a secondary promoter for EF-Tu expression, apparently located within the structural gene for elongation factor EF-G.

Cloning, Molecular↗
PubMed1982

Oversynthesis of elongation factors G and Tu in Escherichia coli.

We induced the oversynthesis of elongation factors Tu and G by using multicopy plasmids carrying the structural genes for these proteins under the control of the lac operator-promoter. We found no evidence that accumulation of excess elongation factor Tu or G affects the expression of genes for ribosomal proteins or elongation factors.

Bacterial Proteins↗
PubMed1981

High-efficiency, temperature-sensitive suppression of amber mutations in Escherichia coli.

We have constructed a high-copy-number plasmid carrying an allele of the supD gene (supD43,74). The plasmid conferred temperature-sensitive suppression of amber mutations. Strains carrying the plasmid exhibited 50 to 60% suppression at 30 degrees C but little or no suppression at 42 degrees C. After a temperature shift from 30 to 42 degrees C the efficiency of suppression decreased gradually over a 60- to 90-min period before reaching the 42 degrees C steady-state level of suppression.

Escherichia coli↗
PubMed1981

New method that uses binding of immunoglobulin A to group A streptococcal immunoglobulin A Fc receptors for demonstration of microbial immunoglobulin A protease activity.

A new method is described for the detection of bacterial immunoglobulin A (IgA) protease which splits IgA into Fab and Fc fragments. The method takes advantage of a recent finding that receptors for IgA fragments occur commonly among type 4 group A streptococci. The bacterial preparation to be tested for protease activity was first incubated with radiolabeled purified IgA1 myeloma protein, and the proportion of radioactivity bound to a standard suspension of the streptococci was then measured. Since isolated Fab fragments do not bind to streptococcal IgA receptors, a decrease in the amount of radioactivity bound to the streptococci, as compared with the amount before digestion, indicates the presence of protease in the test preparation. Using this method, protease activity was detected in Neisseria gonorrhoeae, Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae, and Streptococcus sanguis, but not in Escherichia coli or Branhamella catarrhalis.

Bacteria↗
PubMed1980

Protein L4 of the E. coli ribosome regulates an eleven gene r protein operon.

We have previously reported autogenous regulation of the S10 operon encoding eleven ribosomal proteins. By measuring the synthesis of individual r proteins after specific oversynthesis of nine different ribosomal proteins from the S10 operon, we now find that one, L4, affects the expression of the operon. Moreover, the induction of L4 synthesis results in a strong reduction of the synthesis of mRNA from at least four genes of the S10 operon.

Bacterial Proteins↗