Intracellular localization of long-chain acyl-coenzyme A hydrolase and acyl-L-carnitine hydrolase in brown adipose tissue from guinea pigs.

The activities of long-chain acyl-CoA hydrolase (palmitoyl-CoA hydrolase, EC 3.1.2.2) and long-chain acyl-L-carnitine hydrolase, EC 3.1.1.28) in brown adipose tissue from cold-exposed and control guinea pigs were studied. Mitochondria from cold-exposed animals hydrolysed 21 nmol of palmitoyl-CoA/min per mg of protein and 1.3 nmol of palmitoyl-L-carnitine/min per mg of protein, and the specific activities were respectively 2 and 5 times as high in cold-exposed as in control animals. The subcellular-localization studies showed that both the long-chain acyl-CoA hydrolase and long-chain acyl-L-carnitine hydrolase were localized in the mitochondria. A location also in the soluble fraction cannot be excluded. The long-chain acyl-CoA hydrolase activity was doubled when the mitochondria were disrupted; this indicates that the enzyme is localized in the matrix compartment.     

Dominance and recessiveness at the protein level in mutant x wildtype crosses in Sacchaomyces cerevisiae

Summary The is ₁-locus of the yeast Saccharomyces cerevisiae is the structural gene for threonine dehydratase. is ₁-mutants require isoleucine for growth and do not have active threonine dehydratase.Interallelic complementation is frequent among is ₁-mutants. This is indicative for an aggregate or multimeric structure of yeast threonine dehydratase.Complementing and non-complementing mutants were crossed to wildtype. Properties of threonine dehydratase were assayed in crude extracts of the resulting heterozygotes.Specific activities varied considerably between full wildtype activity and a level about 10% of that. The apparent Michaelis constants were increased in many heterozygotes. This effect was probably due to the aggregation of both mutant and wildtype subunits to form a hybrid threonine dehydratase with reduced substrate affinity in addition to pure wildtype enzyme. This notion is supported by the observation in one heterozygote of two enzyme fractions with increased Michaelis constants in addition to a wildtype-like fraction.The possible formation of hybrid enzymes with normal, reduced or no activity is considered to blur gene dosage relations.A given pair of alleles in a heterozygous cell can generate a new type of enzyme with properties not encountered in the corresponding two homozygous cells. This situation is not accounted for by the classical concepts of dominant-recessive or intermediate behaviour, because the difference between the heterozygotes and the homozygotes is not necessarily only quantitativ but also qualitative.We dedicate this publication to Prof. Dr. C. Auerbach on occasion of her official retirement in admiration for her pioneer work and many contribution to genetics.     

Groundwater promotes emergence of asporogenic mutants of emetic Bacillus cereus

Bacillus cereus is a ubiquitous endospore-forming bacterium, which mainly affects humans as a food-borne pathogen. Bacillus cereus can contaminate groundwater used to irrigate food crops. Here, we examined the ability of the emetic strain B. cereus F4810/72 to survive abiotic conditions encountered in groundwater. Our results showed that vegetative B. cereus cells rapidly evolved in a mixed population composed of endospores and asporogenic variants bearing spo0A mutations. One asporogenic variant, VAR-F48, was isolated and characterized. VAR-F48 can survive in sterilized groundwater over a long period in a vegetative form and has a competitive advantage compared to its parental strain. Proteomics analysis allowed us to quantify changes to cellular and exoproteins after 24 and 72 h incubation in groundwater, for VAR-F48 compared to its parental strain. The results revealed a significant re-routing of the metabolism in the absence of Spo0A. We concluded that VAR-F48 maximizes its energy use to deal with oligotrophy, and the emergence of spo0A-mutated variants may contribute to the persistence of emetic B. cereus in natural oligotrophic environments.     

Vertebrate aristaless-related genes

Aristaless-related genes, a subset of the Paired-related homeobox genes, have in the past few years emerged as a group of regulators of essential events during vertebrate embryogenesis. One group of aristaless-related genes has been linked to the morphogenesis of the craniofacial and appendicular skeleton by their expression patterns and by the phenotypes of natural and artificial mouse mutants. Expression and function in the nervous system characterise a second group, and a third group, the Pitx genes, have been shown to have many different roles, including functions in the pituitary, left-right determination and limb development.