Biomedical subjects

B Theunissen

Publications and source records attributed to B Theunissen.

13 recordsLinked to original sources

PubMed1996

SLS1, a new Saccharomyces cerevisiae gene involved in mitochondrial metabolism, isolated as a syntheticlethal in association with an SSM4 deletion.

SSM4 was isolated as a suppressor of rna14-1, a mutant involved in nuclear mRNA maturation. In order to isolate genes interacting with SSM4, we have searched for mutants that are syntheticlethal in association with an SSM4 deletion. Among the mutants obtained, one, named sls1-1, shows a pet- phenotype. We have cloned and sequenced this gene. It encodes a protein with a calculated molecular mass of 73 kDa. This protein contains a mitochondrial targeting presequence but does not show homology with other known proteins. Deletion of SLS1 does not affect cell viability on glucose but is lethal on a non-fermentable medium. The Sls1p protein does not appear to be involved in mitochondrial DNA replication, transcription, or in RNA splicing maturation or stability. We have also tagged this protein and localized it in mitochondria. Treatment with alkaline carbonate does not extract this protein from mitochondria, suggesting strongly that it is a mitochondrial integral membrane protein. Thus, the SLS1 gene, encodes a mitochondrial integral membrane protein and is paradoxically synlethal in association with a deletion of the SSM4 gene, which encodes an integral nuclear membrane protein.

Amino Acid Sequence↗

PubMed1996

The beginnings of the "Delft tradition" revisited: Martinus W. Beijerinck and the genetics of microorganisms.

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Genetics, Microbial↗

PubMed1994

The role of Glu187 in the regulation of phosphofructokinase by phosphoenolpyruvate.

In bacterial phosphofructokinases, either a glutamic or an aspartic residue is present at position 187, and the mechanism of inhibition by phosphoenolpyruvate seems to be correlated to the nature of residue 187. Upon binding phosphoenolpyruvate, only the enzymes with a Glu187 would undergo a major allosteric conformational change from an active into an inactive state, whereas the enzymes with an Asp187 would only show a simple upward shift in their pH-profile of activity. The phosphofructokinase from Spiroplasma citri, which has an Asp187, has been purified and its properties follow this pattern. The behaviour of mutants of the enzyme from Escherichia coli in which Glu187 is replaced by either aspartate or leucine confirms the importance of residue 187. The major allosteric transition of E. coli phosphofructokinase is abolished by the substitution Glu187-->Asp, suggesting that a glutamate at position 187 is necessary (but not sufficient) for the protein to undergo the change from the active into the inactive state induced by phosphenolpyruvate. In addition, the presence of an acidic residue, aspartate or glutamate, at position 187 is required (but not sufficient) for the binding of ADP (or GDP). This requirement of a negative charge for ADP binding could explain the striking conservation of an aspartate residue at position 187 in all the eukaryotic phosphofructokinases.

Amino Acid Sequence↗

PubMed1994

Knowledge is power: Hugo de Vries on science, heredity and social progress.

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Genetics↗

PubMed1994

Closing the door on Hugo de Vries' Mendelism.

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Austria↗

PubMed1994

[Not Available].

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Genetics↗

PubMed1994

[Not Available].

In the late 19th century bacteriology was a predominantly practical discipline. Beijerinck was among the few workers who engaged in pure microbiological research at this time. He is usually regarded as the 'founding father' of the Delft tradition in chemical bacteriology. Beijerinck's focus, however, was not chemical bacteriology, but heredity and variability in microorganisms. His pertinent views provide an instance of the 19th-century 'developmental' view of heredity and evolution. As for the wider context of Beijerinck's work, there are important similarities between Beijerinck and Hugo de Vries. In the 1890s de Vries became a spokesman for the promotion of pure science as the motor of social progress. His final aim was the improvement of practice. According to Beijerinck, successful practice in microbiology also hinged upon detailed knowledge of heredity and variability. Beijerinck and de Vries were agreed however that scientific research would remain pure; the benefits for practice would follow automatically. Beijerinck did not, decades ahead of others, start a tradition in bacterial chemistry. Nor should he be seen as an early worker groping unsuccessfully around in the confused field of bacterial genetics. In his aproach and problem choice he followed contemporary examples, and he worked within the context of an ideology that was shared by the leading Dutch botanists.

History, 20th Century↗

PubMed1993

[Nature study and happiness in life: Hugo de Vries, Eli Heimans and Jac. P. Thijsse].

This article analyses the backgrounds of Hugo de Vries' stance with regard to the Dutch nature study movement, which rapidly gained momentum in the 1890s. The movement has received little attention from historians until now. A short exposition of its aims and intentions, as envisioned by its main protagonists, Heimans and Thijsse, is provided. It is shown that De Vries' scientific ideas on the improvability of the human species and his liberal social views led him to conclude that both socialism and right-wing 'laisser-faire' ideologies were scientifically unsound. Hereditary theory implied that the human races were genetically stable entities which could not be improved by selection of any kind. The progress of society could only be furthered by placing the emphasis on the individual and its cognitive and social development. According to de Vries, the study of nature provided an excellent means to this end, since it contributed to the individual's personal development as well as to its happiness.

Environment↗

PubMed1993