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Overproduction of Ornithine Decarboxylase in Chinese Hamster Ovary Cells Resistant to Ornithine Analogues.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Overproduction of Ornithine Decarboxylase in Chinese Hamster Ovary Cells Resistant to Ornithine Analogues./
Author:	Choi, Jung Ho.
Description:	1 online resource (117 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 44-07, Section: B.
Contained By:	Dissertations Abstracts International44-07B.
Subject:	Genetics. -
Online resource:	click for full text (PQDT)
ISBN:	9798661741707

Overproduction of Ornithine Decarboxylase in Chinese Hamster Ovary Cells Resistant to Ornithine Analogues.
Choi, Jung Ho.

Overproduction of Ornithine Decarboxylase in Chinese Hamster Ovary Cells Resistant to Ornithine Analogues. - 1 online resource (117 pages)

Source: Dissertations Abstracts International, Volume: 44-07, Section: B.

Thesis (Ph.D.)--University of California, San Diego, 1983.

Includes bibliographical references

Mutants of Chinese hamster ovary cells resistant to millimolar concentrations of (alpha)-methyl- and (alpha)-difluoromethylornithine, inhibitors of ornithine decarboxylase, have been isolated through sequential selections at increasingly higher concentrations of the drugs. The resistant phenotype is completely stable for several weeks in the absence of selection and is dominant in hybrids. The mutants express elevated levels of ornithine decarboxylase activity, in approximate proportion to their level of resistance. By several criteria, such as the rate of degradation in the presence of protein synthesis inhibitors, the affinity for ornithine, inhibition by (alpha)-methylornithine, inhibition by antizyme, and binding of radiolabeled (alpha)-difluoromethylornithine, the enzyme in the mutant cells appears physically unaltered from the enzyme in wild type cells. Regulation of the elevated enzyme activity also appears normal, at least with respect to induction during the cell cycle, repression by polyamines, and induction of antizyme. Indirect evidence from experiments with inhibitors of RNA and protein synthesis suggests that the mutants may have elevated levels of ornithine decarboxylase mRNA. Ornithine decarboxylase from these mutants has been purified to near homogeneity. The major protein species has been positively identified as active enzyme by binding of tritiated inhibitor. Loading the purified protein onto two-dimensional gels has allowed identification of the ornithine decarboxylase spot in similar two-dimensional gels of crude extracts from both mutant and wild type cells. Extracts from mutant cells have an obviously enlarged spot compared to extracts from wild type cells in the position where purified enzyme runs. In future studies, these overproducing mutants should prove invaluable as highly enriched sources of enzyme protein for further enzyme purifications and for analysis of regulation at the level of synthesis and degradation of ornithine decarboxylase.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798661741707Subjects--Topical Terms:

578972
Genetics.
Index Terms--Genre/Form:

554714
Electronic books.

Overproduction of Ornithine Decarboxylase in Chinese Hamster Ovary Cells Resistant to Ornithine Analogues.
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100 1 $a Choi, Jung Ho. $3 1184671
245 1 0 $a Overproduction of Ornithine Decarboxylase in Chinese Hamster Ovary Cells Resistant to Ornithine Analogues.
264 0 $c 1983
300 $a 1 online resource (117 pages)
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500 $a Source: Dissertations Abstracts International, Volume: 44-07, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
502 $a Thesis (Ph.D.)--University of California, San Diego, 1983.
504 $a Includes bibliographical references
520 $a Mutants of Chinese hamster ovary cells resistant to millimolar concentrations of (alpha)-methyl- and (alpha)-difluoromethylornithine, inhibitors of ornithine decarboxylase, have been isolated through sequential selections at increasingly higher concentrations of the drugs. The resistant phenotype is completely stable for several weeks in the absence of selection and is dominant in hybrids. The mutants express elevated levels of ornithine decarboxylase activity, in approximate proportion to their level of resistance. By several criteria, such as the rate of degradation in the presence of protein synthesis inhibitors, the affinity for ornithine, inhibition by (alpha)-methylornithine, inhibition by antizyme, and binding of radiolabeled (alpha)-difluoromethylornithine, the enzyme in the mutant cells appears physically unaltered from the enzyme in wild type cells. Regulation of the elevated enzyme activity also appears normal, at least with respect to induction during the cell cycle, repression by polyamines, and induction of antizyme. Indirect evidence from experiments with inhibitors of RNA and protein synthesis suggests that the mutants may have elevated levels of ornithine decarboxylase mRNA. Ornithine decarboxylase from these mutants has been purified to near homogeneity. The major protein species has been positively identified as active enzyme by binding of tritiated inhibitor. Loading the purified protein onto two-dimensional gels has allowed identification of the ornithine decarboxylase spot in similar two-dimensional gels of crude extracts from both mutant and wild type cells. Extracts from mutant cells have an obviously enlarged spot compared to extracts from wild type cells in the position where purified enzyme runs. In future studies, these overproducing mutants should prove invaluable as highly enriched sources of enzyme protein for further enzyme purifications and for analysis of regulation at the level of synthesis and degradation of ornithine decarboxylase.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2024
538 $a Mode of access: World Wide Web
650 4 $a Genetics. $3 578972
655 7 $a Electronic books. $2 local $3 554714
690 $a 0369
710 2 $a ProQuest Information and Learning Co. $3 1178819
710 2 $a University of California, San Diego. $3 1187935
773 0 $t Dissertations Abstracts International $g 44-07B.
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