The regulatory role of photosystem II photoinactivation and de novo protein synthesis in the degradation and exchange of two forms of the D1 protein in the cyanobacterium Synechococcus PCC 7942

The purpose of this study was to use sodium flufenamate, a compound that inhibits gonadotropin-releasing hormone (GnRH)-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) production in the pituitary, to evaluate the potential role of cAMP as a mediator of GnRH-stimulated gonadotropin secretion from male pituitaries. Quartered male pituitaries were perifused at 37 degrees C and sequential effluent fractions collected every 10 min. Infusions of GnRH resulted in a twofold increase in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion. Cycloheximide, 5 microM, completely inhibited the GnRH-stimulated LH and FSH secretion. Infusions of 0.1 mM flufenamate had similar effects on gonadotropin secretion as cycloheximide, whereas the administration of 5 mM dibutyryl cAMP in combination with GnRH and flufenamate restored the secretory responses of both hormones. The flufenamate-inhibited GnRH stimulated LH and FSH release, which was restored by DBcAMP and appeared to be protein synthesis dependent and specific for cAMP. These results suggest an indirect role for cAMP as a mediator of gonadotropin secretion from male pituitaries. However, in contrast to female pituitaries, the secretion of these hormones from male pituitaries is completely dependent on cAMP and de novo protein synthesis.

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A critical examination of the role of de novo protein synthesis in the osmotic adaptation of the halotolerant alga Dunaliella

FEBS Letters ◽

10.1016/0014-5793(89)81170-6 ◽

1989 ◽

Vol 244 (1) ◽

pp. 93-98 ◽

Cited By ~ 31

Author(s):

Avi Sadka ◽

Amnon Lers ◽

Ada Zamir ◽

Mordhay Avron

Keyword(s):

Protein Synthesis ◽

De Novo ◽

Critical Examination ◽

Osmotic Adaptation ◽

De Novo Protein Synthesis

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Role of de novo protein synthesis in the interconversion of glucose transport systems in the yeast Pichia ohmeri

Biochimica et Biophysica Acta (BBA) - Biomembranes ◽

10.1016/0005-2736(87)90285-9 ◽

1987 ◽

Vol 900 (1) ◽

pp. 139-144 ◽

Cited By ~ 12

Author(s):

R.S. Verma ◽

I. Spencer-Martins ◽

N. Van Uden

Keyword(s):

Protein Synthesis ◽

Glucose Transport ◽

De Novo ◽

Transport Systems ◽

De Novo Protein Synthesis

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Amino Acid Substitutions in the D1 Protein of Photosystem II Affect QB-Stabilization and Accelerate Turnover of D1

Zeitschrift für Naturforschung C ◽

10.1515/znc-1990-0515 ◽

1990 ◽

Vol 45 (5) ◽

pp. 402-407 ◽

Cited By ~ 31

Author(s):

Nir Ohad ◽

Dekel Amir-Shapira ◽

Hiroyuki Koike ◽

Yorinao Inoue ◽

Itzhak Ohad ◽

...

Keyword(s):

Photosystem Ii ◽

D1 Protein ◽

Genetically Engineered ◽

Close Link ◽

Synechococcus Pcc 7942 ◽

Temperature Downshift ◽

The Stability ◽

Pcc 7942 ◽

Isogenic Strains

Abstract Isogenic strains of Synechococcus PCC 7942 were genetically engineered so that copy I of the gene psbA was mutated at specific sites. These mutations resulted in replacements of Ser 264 by Gly or Ala and of Phe 255 by Tyr or Leu in the D1 protein. The mutants were resistant to herbicides inhibiting electron transfer in photosystem II. All mutants exhibited alterations in the stability of QB- as demonstrated by a temperature downshift, to various extents, of the in vivo thermoluminescence emission. Measurements of the light-dependent turnover of D1 showed a marked decrease in the t 1/2 of this protein in the mutants as compared to wild-type, under low to medium light intensities. A correlation was found between the degree of pertur bation in the QB- stability and the rate of acceleration in the turnover of D1. These data pro vide a direct evidence for the overlapping binding sites for the plastoquinone B and herbicides in the D1 protein. In addition these data indicate a close link between QB- destabilization in reaction center II and the mechanism controlling the light-dependent turnover of D1. Based on these results and previous work we suggest that destabilization of the semireduced quinone, facilitates a light-induced damage in D1 which triggers its degradation.

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