肿瘤坏死因子突变体的碘标记及其质量的检测

用Ｉｏｄｏｇｅｎ法对肿瘤坏死因子突变体进行碘标记,用放射纸层析法及自身取代分析法对产物的放化纯度及比放射性活度进行了计算。结果表明：碘的利用率为７２．７６％,纯化后标记物的游离碘为２．１２％,放化纯度为９３．１４％,比放射性活度为１．２ＴＢｑ／ｇ。标记后的肿瘤坏死因子突变体的细胞毒效应只下降４．３８％,提示Ｉｏｄｏｇｅｎ法标记肿瘤坏死因子突变体可获良好效果。     

Structural modification of spindle pole bodies during meiosis II is essential for the normal formation of ascospores in Schizosaccharomyces pombe: Ultrastructural analysis of spo mutants

In order to characterize the morphological steps defined by sporulation (spo) genes during the formation of ascospores in the fission yeast Schizosaccharomyces pombe, we performed an electron microscopic study of the ultrastructure of the spindle pole body (SPB) and of the development of the forespore membrane during the second meiotic division (meiosis II) in sporulation-deficient (spo) mutants (spo4, spo5, spo14 and spo18). No difference was found in terms of the function and the structure of the SPB during the first meiotic division (meiosis I) between the four mutants and wild-type cells. However, during meiosis II, the spo4 and spo18 mutants underwent nuclear division but in neither case were the SPBs modified nor were forespore membranes formed. The SPBs of the spo18 mutant diminished in size after meiosis II and eventually disappeared after 18 h in sporulation medium. By contrast, the SPBs of the spo4 mutant remained unchanged even after an 18-h incubation. The outer plaques of SPBs of spo5 and spo14 mutants were sufficiently modified to allow them to initiate development of the forespore membrane, but the membrane had an abnormally expanded lumen and did not enclose the nuclei during meiosis II. The spo5 mutant produced anucleate spore-like bodies while the spo14 mutant formed unorganized structures with irregular peripheries which, presumably, contained spore-wall precursors, instead of anucleate spore-like bodies. We conclude that the modification of the SPB is essential for the formation of ascospores and at least two genes (spo5 and spo14) participate in the development of the forespore membrane. The defective phenotypes define discrete steps in the development of ascospores, which proceeds via steps defined by the mutant spo4, spo18, spo14 and spo5 genes respectively. Our observations provide further substantial evidence that the SPB plays a pivotal role in the normal development of ascospores in yeasts.     

Rag−mutations involved in glucose metabolism in yeast: Isolation and genetic characterization

Some natural isolates and many laboratory strains of the yeast Kluyveromyces lactis cannot grow on glucose when respiration is inhibited by antimycin A. The ability or inability to grow on glucose in the absence of mitochondrial respiration has been called Rag⁺ or Rag^? phenotype (resistance to antimycin on glucose, respectively). Rag^? strains, unable to grow on glucose in the presence of the respiratory drug, behave as if they were defective in fermentation. The Rag phenotype was first found to be determined by variant alleles of either of the two nuclear genes, RAG1 and RAG2, which code for a low-affinity glucose transport protein and for phosphoglucose isomerase, respectively. These findings suggested that the Rag^? phenotype can be used to obtain mutations of genes involved in glucose metabolism in K. lactis. We thus looked for other Rag^? mutants. Seventy-four mutants were isolated and genetically characterized. All of the mutations were nuclear recessive alleles, defining 11 new complementation groups, which we designate rag3 through rag13.     

XII. Yeast sequencing reports. Sequence,mapping and disruption of CCC1, a gene that cross-complements the Ca2+-sensitive phenotype of csg1 mutants

We have isolated, sequenced, mapped and disrupted a novel gene, CCC1, from Saccharomyces cerevisiae. This gene displays non-allelic complementation of the Ca²⁺-sensitive phenotype conferred by the csg1 mutation. The ability of this gene, in two copies per cell, to reverse the csg1 defect suggests it may have a role in regulating Ca²⁺ homeostasis. The sequence of CCC1 indicates that it encodes a 322 amino acid, membrane-associated protein. The CCC1 gene is located on the right arm of chromosome XII. The sequence has been deposited in the GenBank data library under Accession Number L24112.     

高耐毒性酿酒酵母的紫外诱变选育

木质纤维素生产乙醇已成为世界各国研究开发的热点.但在酿酒酵母对木质纤维素稀酸水解产物的乙醇发酵中,对水解产物中的毒性物质非常敏感.菌种对水解液毒性物质耐受力相对较低是影响木质纤维素乙醇发酵工业化的主要因素之一.利用紫外线对酿酒酵母进行诱变,得到2株高效耐水解液中毒性物质突变株k和n.2株突变株发酵未脱毒的木屑稀酸水解产物的乙醇产量分别达到理论值的71.0%和61.3%,为进一步提高酿酒酵母耐毒性的研究和木质纤维素稀酸水解生产乙醇的工业化提供了基础.     

Increased hydrogen photoproduction by means of a sulfur-deprived Chlamydomonas reinhardtii D1 protein mutant

The photoproduction of H₂ was studied in a sulfur-deprived Chlamydomonas reinhardtii D1 mutant that carried a double amino acid substitution. The leucine residue L159 was replaced by isoleucine, and the asparagine N230 was replaced by tyrosine (L159I-N230Y). Phenotypic characterization of the mutant showed some interesting features compared to its wild type, namely: (1) a lower chlorophyll content; (2) a higher photosynthetic capacity and higher relative quantum yield of photosynthesis; (3) a higher respiration rate; (4) a very high conversion of violaxanthin to zeaxanthin during H₂ production; (5) a prolonged period of H₂ production. In standard conditions, the mutant produced more than 500 ml of H₂, that is, more than one order of magnitude greater than its wild type, and about 5-times greater than the CC124 strain that was used for comparison. The better performance of the mutant was mainly the result of a longer production period. Biogas produced contained up to 99.5% H₂.