A yeast's eye view of mammalian reproduction: cross-species gene co-expression in meiotic prophase

Background  

Meiotic prophase is a critical stage in sexual reproduction. Aberrant chromosome recombination during this stage is a leading cause of human miscarriages and birth defects. However, due to the experimental intractability of mammalian gonads, only a very limited number of meiotic genes have been characterized. Here we aim to identify novel meiotic genes important in human reproduction through computational mining of cross-species and cross-sex time-series expression data from budding yeast, mouse postnatal testis, mouse embryonic ovary, and human fetal ovary.     

Calculation of accurate small angle X-ray scattering curves from coarse-grained protein models

Background  

Genome sequencing projects have expanded the gap between the amount of known protein sequences and structures. The limitations of current high resolution structure determination methods make it unlikely that this gap will disappear in the near future. Small angle X-ray scattering (SAXS) is an established low resolution method for routinely determining the structure of proteins in solution. The purpose of this study is to develop a method for the efficient calculation of accurate SAXS curves from coarse-grained protein models. Such a method can for example be used to construct a likelihood function, which is paramount for structure determination based on statistical inference.     

Block by phencyclidine of acetylcholine and barium induced adrenal catecholamine secretion

Activation of the sympathetic system by phencyclidine (PCP) should result in catecholamine release from the adrenals. However, adrenalectomy does not reduce PCP-induced hypertension. In an attempt to rectify this inconsistency, the direct effects of PCP on the bovine adrenal medulla were examined. At (3×10^?6M), PCP reduced the acetylcholine-(ACh)-induced catecholamine release by 50%. Surprisingly, barium-induced secretion of catecholamines was also reduced by PCP. ACh-induced catecholamine release was not altered by 10^?3M 4-aminopyridine (4 AP), the potassium channel blocker. Thus, calcium antagonist actions of PCP and consequent block of catecholamine secretion from adrenal medulla may explain the lack of effect of adrenalectomy on PCP-induced hypertension. Possible contributions of calcium and/or potassium channel blockade to other manifestations of PCP overdosage are discussed.     

Hydrolysis of dansyl-peptide substrates by leucine aminopeptidase: origin of dansyl fluorescence changes during hydrolysis

The origin of the fluorescence changes observed in stopped-flow experiments of the hydrolysis of three 5-(dimethylamino)naphthalene-1-sulfonyl-(dansyl) peptide substrates by porcine kidney cytosol leucine aminopeptidase has been investigated. The substrates used all have the potential to accept energy from aromatic residues of the enzyme via resonance energy transfer when they are bound as enzyme-substrate complexes, indicating that fluorescence changes due to the buildup and decay of such intermediates are possible. However, the fluorescence of these substrates differs from that of the products, and direct excitation of their dansyl groups during hydrolysis can also be responsible for the observed fluorescence changes due to changes in the concentrations of free substrate and product. The dansyl fluorescence changes observed with excitation wavelengths near 280 nm are not accompanied by quenching of the enzyme fluorescence, as would be expected if there were enzyme-to-substrate energy transfer. The magnitude of the maximal fluorescence change at a fixed concentration of substrate is also independent of the enzyme concentration. Furthermore, the excitation profile for the fluorescence changes shows that they arise from direct excitation of the dansyl group. Thus, there is no energy transfer in these reactions, and the fluorescence changes observed arise from direct excitation of the dansyl group and reflect the instantaneous concentration of substrate. This behavior contrasts sharply with that for the reaction of carboxypeptidase A with dansyl-Gly-Tyr, which has been studied as a positive control for an energy-transfer system.(ABSTRACT TRUNCATED AT 250 WORDS)     

Consequences of thermal change on the myofibrillar ATPase of five freshwater teleosts

Myofibrillar ATPase activity was measured in the epaxial musculature of five freshwater species of fish acclimated to extremes of temperature within their tolerance ranges. Changes in the enzyme activity were apparent in carp, tench and roach, cold acclimated fish (10°C) having higher enzyme activity levels than hot acclimated fish (28°C). Such changes were not apparent in eels or brook trout. Alteration of the enzyme activity took less than 4 weeks, and was totally reversible. This suggests that seasonal adaptation to environmental temperatures is possible, thus maintaining locomotory efficiency.     

Synthesis of N-quinonyltaurines

Summary.  Both 1,4-benzoquinones and 1,4-naphthoquinones were attached to the non-proteinogenic amino acid taurine to form N-quinonyl taurine derivatives. The products were formed via the direct Michael-like addition or by substitution of a good leaving group. An attempt to bridge the two moieties via an ureido spacer resulted in the formation of a bis-quinonylamino isocyanurate derivative. Preliminary MO calculations provided internal ground-state geometries and orbital coefficients of the HOMO levels in two representing taurine conjugates. Received May 6, 2002 Accepted August 13, 2002 Published online December 18, 2002 Acknowledgments This research was supported by the Israel Science Foundation founded by the Academy of Science and Humanities. We wish to thank Ms. Ethel Solomon for skilled technical help. Authors' address: Prof. Shmuel Bittner, Department of Chemistry, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105, Israel, Fax: (972)-8-6472943, E-mail: bittner@bgumail.bgu.ac.il     

Chlamydomonas alpha-tubulin is posttranslationally modified by acetylation on the epsilon-amino group of a lysine

Previous work has shown that the principal alpha-tubulin within Chlamydomonas reinhardtii flagellar axonemes differs from the major alpha-tubulin in the cell body. These two variants of alpha-tubulin are related to one another since posttranslational modification of the cell body form converts it to the axonemal form. When flagella are induced to assemble in the absence of de novo protein synthesis, tritiated acetate can be used to posttranslationally label alpha-tubulin in vivo, and under these conditions, no other flagellar polypeptides exhibit detectable labeling [L'Hernault, S. W., & Rosenbaum, J. L. (1983) J. Cell Biol. 97, 258-263]. In the present report, this labeling method has been used to provide material for chemical analysis of the tritiated moiety that is posttranslationally added to flagellar alpha-tubulin. This radioactivity was volatile after acid hydrolysis, suggesting that the posttranslational modification is the addition of neither an amino acid nor carbohydrate. Treatment of posttranslationally 3H-labeled alpha-tubulin with hydrazine yields radioactive acetylhydrazine, indicating that the moiety involved in posttranslational modification is an acetyl group. Analysis of complete proteolytic digests by thin-layer chromatography has revealed that this acetyl group is located on the epsilon-amino group of a flagellar alpha-tubulin lysine residue.     

Early Inhibition of Acetylcholinesterase and Choline Acetyltransferase Activity in Herpes simplex Virus Type 1 Infection of PC12 Cells

Abstract: Early in the course of productive Herpes simplex virus type 1 (HSV-1) infection of PC12 cells, activities of both acetylcholinesterase (AChE) and choline acetyltransferase (CAT) fell. Studies using metabolic inhibitors and a temperature-sensitive mutant of the virus suggested that the decline in activities of both enzymes was associated with events occurring early in the replicative cycle related to expression of the immediate-early (α) group of viral polypeptides. HSV-1 gene products thus may alter specialized cell functions well before the production of viral progeny and initiation of cell lysis. The early clinical manifestations of nervous system viral infection may reflect focal metabolic disturbance rather than, or in addition to, simple cell death.