Biomedical subjects

G Klug

Publications and source records attributed to G Klug.

59 records · Page 4Linked to original sources

PubMed1985

Gene expression of pigment-binding proteins of the bacterial photosynthetic apparatus: Transcription and assembly in the membrane of Rhodopseudomonas capsulata.

Lowering of oxygen partial pressure in chemotrophic cultures or reduction of light intensity in phototrophic cultures of Rhodopseudomonas capsulata induced formation of the photosynthetic apparatus. A maximum of mRNA coding for the reaction center (RC) and the light-harvesting 1 B870 antenna complex polypeptides occurred 30 min after induction. Maximal expression of mRNA for B800-B850 antenna proteins appeared with a lag time of about 25 min after RC/B870 mRNA. Pigment-binding polypeptides were inserted into the membrane immediately after mRNA synthesis. It is concluded that the delayed formation of the B800-B850 complex compared to the RC and the B870 complex is caused by sequential expression of the corresponding genes. Biological activity of pigment-protein complexes increased after the incorporation of their polypeptides parallel to the maximum of bacteriochlorophyll synthesis. Studies on mutant strains defective in the formation of pigment-protein complexes suggested that pigment synthesis is of importance for assembly of stable complexes.

Journal Article↗

PubMed1984

Construction of a gene bank of Rhodopseudomonas capsulata using a broad host range DNA cloning system.

A gene bank of the phototrophic bacterium Rhodopseudomonas capsulata was constructed using the binary plasmid system pRK290/pRK2013. Fragments of about 20 kb of chromosomal DNA of R. capsulata strain 37b4 were inserted into the cloning vector pRK290. The hybrid plasmids of the gene bank, maintained in Escherichia coli HB101 were transferred by conjugation to R. capsulata strains defective in the photosynthetic apparatus with frequencies of 5 X 10(-4) to 5 X 10(-2). Phototrophically growing transconjugants occurred with frequencies of 5 X 10(-7) to 5 X 10(-6). Recombination between the hybrid plasmids and the R. capsulata chromosome was shown. The hybrid plasmid pRCF1002, carrying a 25 kb insert of R. capsulata wild type DNA, was isolated from one E. coli clone of the gene bank. It reconstituted some bacteriochlorophyll- and photosynthetic negative mutants to phototrophic growth.

Cloning, Molecular↗

PubMed1984

Influence of suspension hypokinesia on rat soleus muscle.

Hindlimb hypokinesia was induced in rats by the Morey method to characterize the response of the soleus muscle. Rats suspended for 1-4 wk exhibited continuous and significant declines in soleus mass, function, and contractile duration. Soleus speeding was in part explained by an alteration in fiber type. The normal incidence of 70-90% type I fibers in the soleus muscle was reduced after 4 wk of suspension to 50% or less in 9 of 11 rats. A significant decline in type I myosin isozyme content occurred without a change in that of type II. Other observed histochemical changes were characteristic of denervation. Consistent with soleus atrophy, there was a significant increase in lysosomal (acid) protease activity. One week of recovery after a 2-wk suspension was characterized by a return to values not significantly different from control for muscle wet weights, peak contraction force, one-half relaxation time, and type I myosin. Persistent differences from control were observed in maximal rate of tension development, contraction time, and denervation-like changes.

Animals↗

PubMed1983

Rapid reduction in parvalbumin concentration during chronic stimulation of rabbit fast twitch muscle.

Chronic indirect stimulation of fast twitch rabbit muscle induced a rapid reduction in parvalbumin concentration. When compared to the unstimulated contralateral muscle, parvalbumins were reduced to 55% following 6 days of stimulation. Prolonged stimulation further reduced parvalbumins so that they were undetectable after 28 days. The time course of these changes appears to be related with the previously observed changes in the sarcoplasmic reticulum.

Animals↗

PubMed1983

Relationships between early alterations in parvalbumins, sarcoplasmic reticulum and metabolic enzymes in chronically stimulated fast twitch muscle.

The present study compares the time courses of the early changes in parvalbumin content, in the properties of the sarcoplasmic reticulum (SR) and in activity and isozyme patterns of metabolic enzymes in chronically (12 h/day) stimulated fast twitch tibialis anterior (TA) muscle of the rabbit. Under the chosen conditions of stimulation, the first significant changes appeared after 6 days. Except for the delayed reduction in pyruvate kinase, the time course of the changes were the same. After 14 days of stimulation, parvalbumin decreased to 37% and Ca2+-ATPase activity of the SR to 29% of normal values. The transformation of the SR was also reflected by a 64% decrease of the 115000-Mr Ca2+-pumping peptide and a 5-fold increase in a 30000-Mr peptide. Following an identical time course, the mitochondrial activities of citrate synthase, 3-hydroxyacyl-CoA dehydrogenase and ketoacid-CoA transferase increased 2.9, 3.0 and 3.7-fold respectively. A similar time course was observed in the M to H-type transition of the lactate dehydrogenase isozymes. The cause of these changes is discussed as it relates to altered transcriptional and/or translational activities. It is suggested that an increase in free intracellular Ca2+ caused by increased contractile activity, which is then perpetuated by the decrease in Ca2+-binding and sequestering capacities, might be the signal for such altered synthetic activities.

Animals↗