A developmental study of rat sperm and testis selenoproteins

Essentially all of the selenium in the rat spermatozoon is bound to a polypeptide of Mr 15,000-17,000 confined to the capsule that surrounds the sperm mitochondria. Isoelectric focussing of isolated 75Se-labelled, carboxymethylated mitochondrial capsule protein (MCP) reveals the presence of at least four radioactive components, with a predominant charge isomer at pI4.6. The sperm selenoprotein appears to be identical with MCP, as judged by the exact coincidence of radioactivity and protein stain during two-dimensional electrophoresis. The temporal pattern of 75Se-labelling of rat caput epididymal spermatozoa after intratesticular 75Se injection suggests that maximum incorporation of 75Se into MCP occurs in step 7-step 12 spermatids and that 75Se uptake ceases during step 15 of spermiogenesis. The developmental appearance of sperm selenoprotein in rat testis therefore appears to lag several days behind that reported for MCP in mouse testis, suggesting the presence of selenium-free MCP in immature germ cells. SDS gel electrophoretic analysis of testis subcellular fractions 24 h after 75Se injection into rat testis at 21, 28 and 90 days of age indicates that sperm selenoprotein first appears in very low concentration during late meiosis and that its concentration increases sharply during early spermiogenesis. Additional 75Se-labelled polypeptides were detected on the gels, most of them of higher molecular weight than MCP. At least two of these (Mr 47,000 and 54,000) displayed a marked decrease in labelling between 5 and 24 h after injection into adult testis, coincident with a comparable increase in 75Se-labelled MCP, indicating that they may be precursors of MCP.     

Sequence of the human erythrocyte phosphoglycerate mutase by microsequencer and mass spectrometry

We have previously reported the isolation in pure form of the human erythrocyte phosphoglycerate mutase isozyme B. We now report the sequence of the whole protein and the identification of its N-terminal blocking group. The protein tryptic peptides of phosphoglycerate mutase isozyme B were isolated by high performance liquid chromatography and their sequence determined by microsequencing. The sequence and the nature of the blocking group of the N-terminal tryptic peptide was shown to be N-acetyl-Ala-Ala-Tyr-Lys by mass spectrometry. Overlaps of the tryptic peptides were obtained by studying the V8 Staphylococcus aureus protease peptides of the aminoethylated phosphoglycerate mutase isozyme B either by microsequencing or by mass spectrometry. The procedure used allowed us to obtain the sequence on a very small amount of material and in a short period of time. Our data agree well with those derived from the cDNA nucleotide sequence described by Sakoda et al. (Sakoda, S., Shanske, S., DiMauro, S., and Schon, E. A. (1988) J. Biol. Chem. 263, 16899-16905). In addition, our data directly indicate that the initiation codon does not introduce a methionine as N-terminal amino acid and allowed the identification of the acetyl N-terminal group.     

Genotype-environment interaction for awn development in isogenic lines of barley

Summary Awn length of four isogenic lines of barley differing by two genes for awn development (A andB) and their short iinkage blocks was evaluated at a wide range of plant densities (0.002 to 3.345 m²/plant) for two years. Awn development was reduced at high plant density. The quarter-awned genotype (aaBB) became phenotypically awnless (aabb) at high plant density. Similar results were obtained each year and the genotype x plant density effect was the major portion of the genotype-environment interaction variance. Additive ( _A , _B ) and additive x additive ( _AB ) gene effects were computed for each plant density for lateral and central floret awn length. For lateral awns _AB was not affected, but _A and _B increased with decreased plant density. In contrast, for central awns _A and _AB decreased and _B increased with decreased plant density.Central floret awns measured at each spike node showed that high plant density reduced awn development most in the lower half of the spike. This is the zone of most rapid awn differentiation and since culm elongation and spike growth rates were greatly increased by high plant density, it was suggested that rapid growth invoked a stress on awn development and differentially altered the expression ofA andB.

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Zusammenfassung An 4 isogenen Gerstenlinien, die sich durch zwei Gene für Grannenbildung (A undB) und entsprechende kurze Kopplungsblocks unterscheiden, wurde zwei Jahre lang die Länge der Grannen bei verschiedener Standdichte (0,002 bis 3,345 m² je Pflanze) untersucht. Bei dichtem Bestand ergab sich eine Beeinträchtigung der Grannenbildung, der viertelbegrannte Genotyp (aaBB) wurde phänotypisch grannenlos (aabb). Die Ergebnisse stimmten in beiden Jahren überein, der Effekt Genotyp x Standdichte hatte den Hauptanteil an der Interaktionsvarianz Genotyp: Umwelt. Additive ( _A , _B ) und additive x additive ( _AB ) Genwirkungen wurden bei jeder Standdichte für die Grannenlänge der Seiten-und Mittelährchen errechnet. Bei den seitlichen Grannen wurde _AB nicht beeinflußt, aber _A und _B erhöhten sich mit abnehmender Standdichte. Im Gegensatz dazu gingen bei den mittleren Grannen _A und _AB zurück, während für _B bei abnehmender Standdichte ein Ansteigen festzustellen war.Messungen der mittleren Grannen jeder Ähre zeigten, daß hohe standdichte der Pflanzen die Grannenbildung am meisten in der unteren Hälfte der Ähre reduzierte. Das ist die Zone, in der sich die Grannen am schnellsten differenzieren, und da die Halm- und Ährenwachstumsraten durch hohe Standdichte stark gesteigert wurden, scheint das schnelle Wachstum auf die Grannenentwicklung hemmend einzuwirken und die Manifestierung vonA undB unterschiedlich abzuändern.

     

Lifetime of bacterial messenger ribonucleic acid

Moses, V. (University of California, Berkeley), and M. Calvin. Lifetime of bacterial messenger ribonucleic acid. J. Bacteriol. 90:1205-1217. 1965.-When cells from a stationary culture of Escherichia coli were placed in fresh medium containing inducer for beta-galactosidase, growth, as represented by increase in turbidity and by total protein synthesis, started within 30 sec. By contrast, beta-galactosidase synthesis was greatly delayed compared with induction during exponential growth. Two other inducible enzymes (d-serine deaminase and l-tryptophanase) and one repressible enzyme (alkaline phosphatase) showed similar lags. The lags were not due to catabolite repression. They could not be reduced by pretreatment of the culture with inducer, or by supplementing the fresh medium with amino acids or nucleotides. The lag was also demonstrated by an i(-) mutant constitutive for beta-galactosidase synthesis. An inhibitor of ribonucleic acid (RNA) synthesis, 6-azauracil, preferentially inhibited beta-galactosidase synthesis compared with growth in both inducible and constitutive strains. Puromycin, an inhibitor of protein synthesis, acted as an inhibitor at additional sites during the induction of beta-galactosidase synthesis. No inhibition of the reactions proceeding during the first 20 sec of induction was observed, but puromycin seemed to prevent the accumulation of messenger RNA during the period between 20 sec and the first appearance of enzyme activity after 3 min. It is suggested that these observations, together with many reports in the literature that inducible enzyme synthesis is more sensitive than total growth to some inhibitors and adverse growth conditions, can be explained by supposing that messenger RNA for normally inducible enzymes is biologically more labile than that for some normally constitutive proteins. The possible implications of this hypothesis for the achievement of cell differentiation by genetic regulation of enzyme synthesis are briefly discussed.     

Aggregation and the maintenance of genetic diversity: An individual-based cellular model

Summary A cellular model, where each individual is explicitly defined, is used to describe a population of a mycophagous species ofDrosophila. Patches represent single fungal fruiting bodies which are only available as oviposition sites for a single fly generation. Standard competition equations are used to describe the interaction between larval genotypes at each patch. Dispersal of adults is obligatory and uses a simple model of patch choice to produce aggregated arrivals of adults at fresh patches. The degree to which aggregation of adults and eggs can promote coexistence of genotypes in a one-locus, two-allele system with dominance is explored. When both phenotypes (A- andaa) are aggregated, a polymorphism can be maintained for over 1000 generations even when the selective disadvantage of one phenotype (aa) is great. This model enhances the degree of polymorphism in a population, using aggregation. It does not preclude the operation of other methods which enhance the coexistence of genotypes. Therefore, it is acting to augment the degree of polymorphism maintained in species which exploit patchy and ephemeral habitats, including allDrosophila and a wide range of other organisms.