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J L Gibson

Publications and source records attributed to J L Gibson.

At least 37 records · Page 2Linked to original sources
PubMed1991

Nucleotide sequence, transcriptional analysis, and expression of genes encoded within the form I CO2 fixation operon of Rhodobacter sphaeroides.

In Rhodobacter sphaeroides, many of the structural genes encoding enzymes of the Calvin cycle are duplicated and grouped within two separate clusters. In this study, the nucleotide sequence of a 5627-base pair region of DNA that contains the form I Calvin cycle gene cluster has been determined. The five open reading frames are arranged in the order, fbpA prkA cfxA rbcL rbcS and are tightly linked and oriented in the same direction. The results of insertional mutagenesis studies suggest the genes are organized within an operon. Consistent with this proposal, the cfxA gene has been tentatively identified as a gene encoding the Calvin cycle enzyme, aldolase. Measurement of the activities of various Calvin cycle enzymes in the insertion mutants showed that inactivation of genes within one CO2 fixation cluster affected expression of genes within the second cluster, revealing a complex regulatory network.

Amino Acid Sequence↗
PubMed1990

Rat cholesterol side-chain cleavage cytochrome P-450 (P-450scc) gene. Structure and regulation by cAMP in vitro.

The entire rat P-450scc gene has been cloned, positions/sequences of the exon-intron boundaries (I-IX) are described and 940 base pairs (bp) of 5'-flanking DNA have been sequenced, compared to mouse, bovine and human genes, and analyzed by functional assays. Primer extension analysis mapped the transcription start site 32 bp upstream of the initiator methionine codon. The rat P-450scc promoter was ligated to the human growth hormone (GH) gene yielding p-940RsccGH. This rat P-450scc fusion gene and a mouse gene (p-1500MsccGH) were transiently transfected into primary cultures of rat granulosa cells and Y1 adrenal cells. In the Y1 cells primer extension analysis showed that the rat P-450sccGH gene was expressed at lower basal levels than that of the mouse gene but showed greater stimulation (4-8-fold) in response to 8-bromo-cyclic AMP than the mouse (3-4-fold). Similar results were obtained when the fusion genes were transfected into primary cultures of rat granulosa cells and production of GH was measured in the media of the cells stimulated with forskolin. Furthermore, we document that gonadotropins (follicle-stimulating hormone/luteinizing hormone) can induce luteinization of granulosa cells in vitro, that this process is associated with constitutive maintenance of P-450scc mRNA in the absence of hormones/cAMP, that these events associated with luteinization are differentiation-stage specific and occur only in granulosa cells of preovulatory follicles but not in small antral follicles, that the process can be inhibited by cycloheximide if the protein synthesis inhibitor is present during the first 6 h of exposure to luteinizing hormone but not if added for short durations (3-5 h) later, and that once luteinization is induced P-450scc mRNA expression and progesterone biosynthesis are not strictly dependent on cAMP. Thus, the P-450scc gene is regulated by both cAMP-dependent and cAMP-independent mechanisms, each of which are associated with a specific stage of granulosa cell differentiation. The DNA domains involved in regulating these two diverse processes remain to be determined. Although there was remarkable sequence homology among rat, mouse, bovine, and human genes within 70 bp of the transcriptional start site, no other sequence similarities revealed conserved functional domains among the four genes. Although some cAMP-responsive element-like sequences are present in the rat gene, these were not conserved in the other species; including the mouse which showed high sequence homology with the rat throughout 900 bp of 5'-flanking DNA. Thus, the cAMP domains specific to this and other steroidogenic genes remain to be clearly identified.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1990

The form II fructose 1,6-bisphosphatase and phosphoribulokinase genes form part of a large operon in Rhodobacter sphaeroides: primary structure and insertional mutagenesis analysis.

Fructose 1,6-bisphosphatase (FBPase) and phosphoribulokinase (PRK) are two key enzymes of the reductive pentose phosphate pathway or Calvin cycle of photosynthetic carbon dioxide assimilation. Early studies had indicated that the properties of enzymes isolated from photosynthetic bacteria were clearly distinct from those of enzymes obtained from the chloroplasts of higher plants [for a review, see Tabita (1988)]. The eucaryotic enzymes, which are light activated by the thioredoxin/ferredoxin system (Buchanan, 1980), were each shown to contain a putative regulatory amino acid sequence (Marcus et al., 1988; Porter et al., 1988). The enzymes from photosynthetic bacteria are not controlled by the thioredoxin/ferredoxin system but exhibit complex kinetic properties and, in the case of PRK, there is an absolute requirement of NADH for activity. In the photosynthetic bacterium Rhodobacter sphaeroides, the structural genes of the Calvin cycle, including the genes that encode FBPase (fbp) and PRK (prk), are found in two distinct clusters, and the fbp and prk genes are closely associated in each cluster. In the present investigation, we have determined the nucleotide sequence of the fbpB and prkB genes of the form II cluster and have compared the deduced amino acid sequences to previously determined sequences of light-activated enzymes from higher plants and from other eucaryotic and procaryotic sources. In the case of FBPase, there are several regions that are conserved in the R. sphaeroides enzymes, including a protease-sensitive area located in a region equivalent to residues 51-71 of mammalian FBPase.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

Recent studies on the molecular biology and biochemistry of CO2 fixation in phototrophic bacteria.

Rhodobacter sphaeroides was found to contain two clusters of chromosomally encoded CO2 fixation structural genes. Recent studies indicate that genes within each cluster are cotranscribed, suggesting that there is a single long transcript for each cluster. All of the genes have been sequenced, homologies noted, specific mutations obtained, and interesting upstream regulatory sequences found. Site-directed mutagenesis studies of the Anacystis rbcS has begun to provide information relative to RubisCO structure and function. In addition, RubisCO-negative strains of photosynthetic bacteria have been constructed to screen for altered RubisCO sequences.

Base Sequence↗
PubMed1989

A single-blind, placebo-controlled study of glycosaminoglycan-peptide complex ('Rumalon') in patients with osteoarthritis of the hip or knee.

A randomized, single-blind, placebo-controlled trial was carried out in 62 patients (30 with osteoarthritis of the hip, 32 with osteoarthritis of the knee) to examine the efficacy of glycosaminoglycan-peptide complex in the treatment of osteoarthritis. Patients received 8-week courses of trial medication, each consisting of intramuscular injections of 3 x 2 ml ampoules per week, alternating with 8-week periods free of trial medication, in addition to conventional drug therapy and physiotherapy, as required. After 2-years' treatment, glycosaminoglycan-peptide-treated patients showed significant improvements, as compared with placebo, in relation to night pain, pain during the day, joint mobility and walking ability. Similar results were seen with both osteoarthritis of the hip and knee. In osteoarthritis of the knee it was also possible to assess joint swelling and this also showed a significant improvement. There were no significant changes in range of joint movement except for a significant decrease in active flexion in the patients with osteoarthritis of the knee treated with placebo. In contrast with many anti-osteoarthritic drugs, glycosaminoglycan-peptide complex was very well tolerated. These results suggest that glycosaminoglycan-peptide complex may be a valuable alternative form of long-term therapy for patients with osteoarthritis.

Aged↗
PubMed1988

Localization and mapping of CO2 fixation genes within two gene clusters in Rhodobacter sphaeroides.

Two fructose 1,6-bisphosphatase structural genes (fbpA and fbpB) have been identified within two unlinked gene clusters that were previously shown to contain the Rhodobacter sphaeroides sequences that code for form I and form II ribulose 1,5-bisphosphate carboxylase-oxygenase and phosphoribulokinase. The fbpA and fbpB genes were localized to a region immediately upstream from the corresponding prkA and prkB sequences and were found to be transcribed in the same direction as the phosphoribulokinase and ribulose 1,5-bisphosphate carboxylase-oxygenase genes based on inducible expression of fructose 1,6-bisphosphatase activity directed by the lac promoter. A recombinant plasmid was constructed that contained the tandem fbpA and prkA genes inserted downstream from the lac promoter in plasmid pUC18. Both gene products were expressed in Escherichia coli upon induction of transcription with isopropyl beta-D-thiogalactoside, demonstrating that the two genes can be cotranscribed. A Zymomonas mobilis glyceraldehyde 3-phosphate-dehydrogenase gene (gap) hybridized to a DNA sequence located approximately 1 kilobase upstream from the form II ribulose 1,5-bisphosphate carboxylase-oxygenase gene. Although no corresponding gap sequence was found within the form I gene cluster, an additional region of homology was detected immediately upstream from the sequences that encode the form I and form II ribulose 1,5-bisphosphate carboxylase-oxygenases.

Carbon Dioxide↗
PubMed1987

Organization of phosphoribulokinase and ribulose bisphosphate carboxylase/oxygenase genes in Rhodopseudomonas (Rhodobacter) sphaeroides.

A heterologous phosphoribulokinase (PRK) gene probe was used to analyze two recombinant plasmids isolated from a Rhodopseudomonas (Rhodobacter) sphaeroides gene library. These plasmids were previously shown to carry the genes for form I and form II ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBPC/O). Southern blot hybridization analysis indicated that there were two PRK genes linked to the RuBPC/O coding sequences. Restriction mapping showed the arrangement of the duplicate sets of PRK and RuBPC/O to be distinct. Subcloning of the hybridizing PRK sequences downstream of the lac promoter of pUC8 allowed expression of the two PRK enzymes in Escherichia coli. Analysis of the purified proteins by sodium dodecyl sulfate-slab gel electrophoresis revealed polypeptides with molecular weights of 32,000 and 34,000 corresponding to the form I and form II PRKs, respectively. Preliminary experiments on sensitivity to NADH regulation suggested that the two PRK enzymes differ in catalytic properties.

Cloning, Molecular↗
PubMed1986

Isolation of the Rhodopseudomonas sphaeroides form I ribulose 1,5-bisphosphate carboxylase/oxygenase large and small subunit genes and expression of the active hexadecameric enzyme in Escherichia coli.

A library of cloned Rhodopseudomonas sphaeroides DNA was screened by colony hybridization for form I ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBPC/O) sequences using heterologous RuBPC/O probes. A recombinant plasmid was identified that hybridized to both the Anacystis nidulans and the R. sphaeroides form II RuBPC/O genes. Subcloning of a hybridizing 4-kb SmaI fragment allowed expression of active enzyme in Escherichia coli that was identical to form I RuBPC/O based on polyacrylamide gel electrophoresis and Western immunoblot analysis.

DNA Restriction Enzymes↗
PubMed1985

Structural differences in the catalytic subunits of form I and form II ribulose 1,5-bisphosphate carboxylase/oxygenase from Rhodopseudomonas sphaeroides.

There are significant differences in the large subunits of form I and form II ribulose 1,5-bisphosphate carboxylase/oxygenase isolated from Rhodopseudomonas sphaeroides. Two-dimensional peptide mapping of carboxymethylated large subunits clearly indicates that there are differences in the primary structure of the two proteins. These results are supported by limited proteolysis with three different proteases and by subsequent analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These data, in conjunction with immunological studies and investigations on the regulation of the two enzymes, support the conclusion that the large subunits of form I and form II ribulose 1,5-bisphosphate carboxylase/oxygenase may be different gene products.

Amino Acids↗
PubMed1980

Marital relationships, evaluations of spouse and self, and anxiety.

Questionaire data were gathered from 164 married couples to test hypotheses that husbands' and wives' anxiety levels will be low to the extent that: (a)they share decision-making power, share household role responsibilities, and express high maritial solidarity; and (b) they hold positive evaluations of one another, perceive positive reactions from one another, and show positive self-evaluations. The first hypothesis was supported only for solidarity. The second hypothesis received strong support for husbands and wives. For wives, solidarity was the strongest predictor of anxiety, while self-evaluation was the most important factor for husbands.

Adult↗
PubMed1979

Activation of ribulose 1,5-bisphosphate carboxylase from Rhodopseudomonas sphaeroides: probable role of the small subunit.

The activation properties of the form I and form II ribulose 1,5-bisphosphate carboxylases from Rhodopseudomonas sphaeroides were examined. Both enzymes have a requirement of Mg2+ for optimal activity. Mn2+, Ni2+, and Co2+ can also support activity of the form I enzyme, whereas only Mn2+ can substitute for Mg2+ with the form II enzyme. The effect of different preincubations on the carboxylase reaction was also examined. Both enzymes exhibited a lag when preincubated with other than Mg2+ and CO2 before assay, but the lag was much more pronounced and the rate of the reaction was slower with the form I enzyme under these conditions. Activation of the form I carboxylase By Mg2+ and CO2 occurred more rapidly than that of the form II enzyme. The results obtained with the two distinct forms of carboxylase from R. sphaeroides, as well as studies with the spinach and Rhodospirillum rubrum enzymes, thus indicate that the presence of the small subunit affects the rate of activation by Mg2+ and CO2 as well as the rate of reactivation of ribulose bisphosphate-inactivated enzyme.

Anaerobiosis↗
PubMed1977

Different molecular forms of D-ribulose-1,5-bisphosphate carboxylase from Rhodopseudomonas sphaeroides.

Ribulose-1,5-bisphosphate (Rbu-P2) carboxylase isolated from Rhodopseudomonas sphaeroides 2.4.1.Ga was separated into two different forms by DEAE-cellulose column chromatography. Both forms, designated Peak I and Peak II have been purified to homogeneity by the criterion of polyacrylamide disc-gel electrophoresis. The Peak I carboxylase has a molecular weight of 550,000, while the Peak II carboxylase is a smaller protein having a molecular weight of approximately 360,000. Sodium dodecyl sulfate electrophoresis revealed a large subunit for both enzymes which migrates similarly to the large subunit of spinach Rbu-P2 carboxylase. The Peak I enzyme also exhibited a small subunit having a molecular weight of 11,000. No evidence for a smaller polypeptide was found associated with the Peak II enzyme. Antisera prepared against the Peak I enzyme inhibited Peak I enzymatic activity, but had no effect on the activity of the Peak II enzyme. The two enzymes exhibited marked differences in catalytic properties. The Peak I enzyme exhibits optimal activity at pH 8.0 and is inhibited by low concentrations of 6-phosphogluconate, while the Peak II enzyme has a pH optimum of 7.2 and is relatively insensitive to 6-phosphogluconate.

Carboxy-Lyases↗
PubMed1977

Isolation and preliminary characterization of two forms of ribulose 1,5-bisphosphate carboxylase from Rhodopseudomonas capsulata.

The presence of two distinct forms of ribulose 1,5-bisphosphate carboxylase has been demonstrated in extracts of Rhodopseudomonas capsulata, similar to the form I (peak I) and form II (peak II) carboxylases previously described from R. sphaeroides (J. Gibson and F. R. Tabita, J. Biol. Chem 252:943-949, 1977). The two activities, separated by diethylaminoethyl-cellulose chromatography, were shown to be of different molecular size after assay on polyacrylamide gels. The higher-molecular-weight carboxylase from R. capsulata was designated form I-C, whereas the smaller enzyme was designated form II-C. Catalytic studies revealed significant differences between the two enzymes in response to pH and the effector 6-phosphogluconate. Immunological studies with antisera directed against the carboxylases from R. sphaeroides demonstrated antigenic differences between the two R. capsulata enzymes; cross-reactivity was observed only between R. sphaeroides anti-form II serum and the corresponding R. capsulata enzyme, form II-C.

Antigens, Bacterial↗
PubMed1976

Carbon dioxide assimilation in blue-green algae: initial studies on the structure of ribulose 1,5-bisphosphate carboxylase.

D-Ribulose 1,5-bisphosphate carboxylase was purified from the blue-green alga Anabaena cylindrica (Lemm) by procedures involving acid precipitation, ammonium sulfate fractionation, and Sephadex G-200 gel filtration. The enzyme was homogeneous by the criterion of polyacrylamide disc gel electrophoresis and was a multimer of a single-size polypeptide chain of 54,000 daltons. The carboxylases from four species of blue-green algae (Anabaena, Nostoc strain MAC, Agmenellum quadruplicatum strain PR-6, and Anacystis nidulans strain TX20) were closely similar in molecular size, since enzyme activity was eluted at the same volume after sucrose gradient centrifugation. Further analysis by gel filtration indicated that the four blue-green algal carboxylases were nearly identical in molecular weight, ranging from 449 to 453,000. The amino acid composition of the Anabaena carboxylase was determined and was found to resemble closely the composition of the large subunit from eukaryotic photosynthetic organisms.

Amino Acids↗