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Biomedical subjects

G S Groot

Publications and source records attributed to G S Groot.

At least 37 records · Page 2Linked to original sources
PubMed1976

The cytochrome bc1 complex of yeast mitochondria. Isolation and partial characterization of the cytochrome bc1 complex and cytochrome b.

We have isolated the cytochrome bc1 complex and some of its constituent polypeptides from bakers yeast and have studied its spectroscopy, electrophoresis and amino acid analysis. The isolated complex contained 6 mumol of b heme and approximately 3 mumol of c1 heme per g of protein. The electron paramagnetic resonance spectrum was similar to that of the beef-heart preparation. The complex consisted of 7 polypeptides with mobilities on sodium dodecylsulphate polyacrylamide gel electrophoresis corresponding to Mr 44,000, 40,000, 32,000, 32,000, 17,000, 14,000 and 11,000. One of the polypeptides with Mr 32,000 was identified on sodium dodecylsulphate gels as cytochrome c1 by porphyrin fluorescence. Cytochrome b was isolated from the complex by treating it with guanidine hydrochloride; it had a purity of 20 mumol per g of protein and consisted of a polypeptide with Mr 32,000 plus two minor bands with Mr 14,000 and 11,000. We have isolated the polypeptide of Mr 32,000 from cytochrome b and the polypeptides of Mr 44,000 and 40,000 ("core proteins") from the complex, both by preparative sodium dodecylsulphate gel electrophoresis and determined their amino acid composition. Only the b polypeptide of Mr 32,000 shows the low proportion of polar amino acid residues that is considered typical of membrane proteins.

Adenosine Triphosphatases↗
PubMed1975

Sequence homology of nuclear and mitochondrial DNAs of different yeasts.

1. Both nuclear and mtDNA of four different yeasts show approximately 10% homology as measured by DNA-DNA filter hybridization. These homologous sequences are mainly attributable to the ribosomal cistrons. 2. Melting curve analysis shows that the heterologous mitochondrial DNA-DNA hybrids contain several times more mismatching than the nuclear DNA-DNA hybrids. 3. DNA-rRNA hybridization shows that the sequences of the ribosomal cistrons in both the nuclear and the mitochondrial genome have been conserved during evolution. 4. However, melting curve analysis of the DNA-RNA hybrids shows that the sequence of the nuclear ribosomal cistrons have undergone considerable fewer nucleotide substitutions than their mitochondrial counterparts. 5. The results suggest that the mitochondrial ribosomal cistrons have evolved more rapidly than the nuclear cistrons. This is discussed in the light of theories on the rat of molecular evolutin.

Base Sequence↗
PubMed1975

Biosynthesis of polypeptides of cytochrome c oxidase by isolated mitochondria.

Yeast mitochondria, incubated with radioactive amino acids in a "protein-synthesizing mixture" containing an oxidizable substrate and an ATP regenerating system, have been shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to incorporate label into polypeptides equivalent in molecular weight and relative amount ot those made in vivo in the presence of cycloheximide. The ability of these isolated mitochondria to synthesize "native" polypeptides was assessed by examining the incorporation of label into subunits of cytochrome c oxidase (EC 1.9.3.1). An analysis of immunoprecipitates formed by incubating cholate extracts of labeled mitochondria with an antiserum against holocytochrome c oxidase revealed that label was incorporated into three polypeptides of sizes equivalent to those of cytochrome c oxidase subunits I, II, and III, shown from earlier studies in vivo to be translated on mitochondrial ribosomes. Further evidence that these polypeptides made in vitro are "native" and identical to subunits I, II, and III was provided by the observation that labeled polypeptides equivalent in size to subunits I-III- ARE ALSO IMMUNO-PRECIPITATED BY ANTISERUM AGAINST SUBUNITS V plus VII, an antiserum that can precipitate subunits I, II, and III only when they are complexed to the cytoplasmically synthesized subunits, V and VII, of the enzyme. These results suggest that isolated mitochondria are capable of synthesizing three subunits of cytochrome c oxidase and assembling them into a holoenzyme.

Chloramphenicol↗
PubMed1971

Promitochondria of anaerobically grown yeast. V. Energy transfer in the absence of an electron transfer chain.

Promitochondria of anaerobically grown Saccharomyces cerevisiae lack cytochromes aa(3), b, c(1), and c, as well as ubiquinone, yet catalyze a P(i)-ATP exchange reaction that is sensitive to uncouplers, rutamycin, and atractyloside. The promitochondrial P(i)-ATP exchange reaction is abolished by the cytoplasmic "petite" mutation, as well as by growth of the cells in the presence of erythromycin, which indicates a role of mitochondrial protein synthesis in the assembly of the energy transfer system. These observations demonstrate that mitochondrial energy transfer can occur in the absence of a respiratory chain.

Cell Membrane Permeability↗