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THE ROLE OF ZINC HOMEOSTASIS IN THE PHENOTYPE OF A PLEIOTROPIC NEUROSPORA MUTANT

A class of Neurospora crassa mutants that display the phenotype of ultraviolet light sensitivity, histidine sensitivity, accelerated mitotic recombination, and meiotic self-incompatibility were found to have impaired zinc accumulation. This may result in the formation of the pleiotropic phenotype. Since the original description of the mutant class several additional characteristics have been added including: extra-cellular nuclease deficiency, radiomimetic chemical sensitivity, amino acid transport deficiency, cell surface (gamma)-glutamyl transpeptidase deficiency, and extracellular azo reductase amplification. / The extreme divergence exhibited by the mutants implicated some fundamental mechanism of cellular control. This investigation grew from the observation that many of the enzymes involved with the phenotype were associated with zinc or copper metabolism. In comparison to wildtype the mutant was found to have a 50% reduction in ('65)zinc accumulation. The affected transport system apparently also transports Cu('+2). Zinc binding proteins in wildtype and mutant cells were examined. Two Zn('+2) binding proteins of similar low molecular weight and charge were purified from the wildtype and the mutant strain. Copper failed to bind to the zinc metallothionein-like proteins. The kinetics of zinc and copper accumulation suggest that high concentrations of copper inhibit zinc accumulation. One of the binding proteins, zinc metallothionein II, was not expressed in the mutant at physiological concentrations of zinc in media, but could be induced with high concentrations of the metal. The two metallothioneins exhibit amino acid compositions that are cysteine rich and lack aromatic amino acids and histidine, have a molecular weight of approximately 6,500; and therefore, they are similar to mammalian metallothioneins. / A model is proposed whereby zinc metallothionein II in uvs-6 is not expressed at physiological concentrations of zinc which results in impaired zinc metabolism. The enzymes of nitrogen metabolism are particularly affected by the change in zinc homeostasis. / Source: Dissertation Abstracts International, Volume: 45-04, Section: B, page: 1112. / Thesis (Ph.D.)--The Florida State University, 1984.

Identiferoai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75323
ContributorsPEGG, RANDALL KEVIN., Florida State University
Source SetsFlorida State University
Detected LanguageEnglish
TypeText
Format119 p.
RightsOn campus use only.
RelationDissertation Abstracts International

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