Regulation of the psbA multigene family in the cyanobacterium Synechococcus sp. strain PCC 7942 /
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| Other Authors: | , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1989.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=746621401&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Abstract: | The genome of the cyanobacterium Synechococcus sp. strain PCC 7942 contains three psbA genes encoding two forms of the D1 protein; form I, the product of psbAI, differs from form II, the product of both psbAII and psbAIII, at 25 of 360 amino acid residues. Translational gene fusions between each of the Synechococcus psbA genes and the Escherichia coli lacZ gene were inserted into the chromosome of wild-type and psbAmutant strains of Synechococcus at the respective psbA loci to serve as in vivo reporters of psbA expression. β-Galactosidase activities measured in the transformed strains indicated differential expression of the psbA-lacZ fusions in response to light availability. As light intensity decreased from 600 [symbols in PDF], expression of the psbAI reporter increased 700% while expression of the psbAII and psbAIII reporters decreased 90%, suggesting differential production of the two forms of D1 in photosystem II in response to light availability. Inactivation of specific psbA genes in the reporter strains resulted in altered β-galactosidase activities, suggesting an interactive regulatory mechanism among the three psoA genes. Antisera were raised against purified hybrid proteins encoded by psbAI-lacZ and psbAlil-iacZ translauonal gene fusions that contain the unique termini of D1 form I and form II, respectively. Western analysis of thylakoid membranes from wild-type cells cultured at different light intensities detected both forms of D1 in the membranes and showed changes in the ratio of the two forms. The D1 composition of the membrane matched predicted ratios of the two forms based on (3-gaiactosidase activities of the reporter strains: as light intensity decreased from 482 [symbols in PDF] 1, the amount of form I increased 58%, while the amount of form II decreased 60%. Dl form I was maximally detected in membranes from ceils harvested at all light intensities below 390 [symbols in PDF], whereas form II was maximally detected at high light intensities, suggesting that form II serves a role in adaptation to a high light environment. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Biochemistry." |
| Physical Description: | xi, 122 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |